Claude vs ChatGPT vs Gemini vs Perplexity: which AI model to choose in 2026?

In early September 2026, three new models came out in three days: Claude Fable 5.1 on 1 September, Gemini 3.8 Flash on 2 September and GPT-6 Astra on 3 September. If you chose an AI subscription over the summer, it is worth taking another look. We set ChatGPT, Claude, Gemini and Perplexity side by side as they stand on 12 September 2026, with every claim checked with the maker or an independent source. The short answer: there is no winner for everything. Which AI fits depends mostly on your tasks and on the software your team works in.

Want to use AI structurally in your business? ClickForest helps Flemish SMEs in Mechelen, Antwerp and the rest of Flanders through AI for growth, from training to a working application.

Which AI is the best in September 2026?

There is no winner for everything. On the independent Artificial Analysis Intelligence Index, Claude Fable 5.1 and GPT-6 Astra share first place with 53 points, but Astra does it at an average of 57% less per task. On LMArena, where users compare answers blind, a Claude model is at the top.

For a business, that ranking rarely decides it. What matters more is the software your team works in and what you want to do with the tool. This is the quick choice:

How to combine the four tools in your work is covered in the superpowers of ChatGPT, Claude, Gemini and Perplexity. A broader overview for marketing teams is in our list of AI tools for marketers.

Which new AI models came out in September 2026?

Three in three days. Anthropic launched Claude Fable 5.1 on 1 September, Google Gemini 3.8 Flash on 2 September and OpenAI GPT-6 Astra on 3 September. Alongside Fable 5.1 came Claude Mythos 5.1: the same model with different safeguards, which for now only a limited group of US organisations get. Gemini 3.5 Pro, which Google has been announcing for a while, is not here yet.

The summer was already busy. These are the releases since late June that matter:

Google’s missing Pro model stood out. Thomas Claburn wrote in The Register:

“Google CEO Sundar Pichai’s reassurances weren’t particularly convincing in light of the company’s failure to release Gemini 3.5 Pro in June as promised.”

— Thomas Claburn, The Register, September 2026

Google itself wrote on 21 July that 3.5 Pro is being tested with partners and will become broadly available “as soon as it’s ready” (Google, July 2026).

What is the difference between ChatGPT, Claude, Gemini and Perplexity?

ChatGPT offers plans from free to Pro and features such as Work, Sites and deep research, Claude is built around agents that finish work on their own, Gemini is built into Google Workspace and also reads video and audio, and Perplexity searches the web and answers with sources. ChatGPT and Claude now also search the web live, so being up to date no longer makes Perplexity unique on its own.

1. ChatGPT: GPT-6 Astra, Work and Sites

OpenAI announced GPT-6 Astra on 3 September 2026 and is rolling it out in phases (OpenAI, September 2026). On 12 September, Astra is in the chat for Pro, Business and Enterprise; Plus gets it for now only in ChatGPT Work and Codex (help center, September 2026). On Enterprise it was off by default at launch (OpenAI). So if you use Plus, you talk to GPT-5.6 Sol in the regular chat. On Free and Go, that is GPT-5.6 Luna.

Independent developer Simon Willison saw it like this on launch day:

“This is clearly OpenAI’s Fable competitor, and appears to score higher than Fable on most of OpenAI’s self-reported benchmarks.”

— Simon Willison, independent developer and blogger, September 2026

Note the word self-reported: on the independent Artificial Analysis index, Astra and Fable 5.1 are now level. Greg Kamradt of the ARC Prize Foundation called Astra “the best model we’ve ever tested”, but that quote is on OpenAI’s own launch page. Willison also made a practical point: “OpenAI may have vanquished one of the ongoing challenges with long context processing” (simonwillison.net).

Beyond the models, ChatGPT runs on features: ChatGPT Work, Sites, deep research, scheduled tasks and a built-in browser (pricing page). The context window depends on your plan, from 27,000 tokens in the free Instant mode to 400,000 in Pro’s reasoning mode. Background on the previous generation is in our ChatGPT 5 guide.

2. Claude: Fable 5.1 for heavy work, Opus 5 as the workhorse

Anthropic released Claude Fable 5.1 on 1 September 2026, together with Mythos 5.1. According to Anthropic they are “the same model, but with different levels of safeguards”: Fable 5.1 is generally available, Mythos 5.1 only through programmes for cybersecurity and life sciences, and for now “only available to a set of US organizations” (Anthropic, September 2026).

Fable 5.1 is not in every plan. On Max it may use up to half of your weekly limit, on Enterprise it is included, on Pro only through extra usage credits, and on Free and Team not at all (pricing page). At launch, Anthropic made Sonnet 5 the default on Free and Pro (30 June) and Opus 5 the default on Max and the strongest model on Pro (24 July). If you are unsure, Anthropic itself gives this advice: “start with Claude Opus 5 for most workloads. Use Claude Fable 5.1 for demanding reasoning and long-horizon agentic work” (Anthropic).

The editors of The Neuron tested Fable 5.1 live and noticed above all a shift in what you leave to such a model:

“The surprise was how quickly the question changed from “Can it do this?” to “How much judgment should we let it exercise without asking us first?””

— The Neuron editorial team, September 2026

Claude is strongly focused on work an agent finishes on its own. Claude Cowork completes tasks in your files, Claude in Chrome operates your browser and Claude Code writes software (see vibe coding versus Claude Code). How the desktop app bundles those modes is covered in Claude Desktop explained. Do mind the context window: in the apps it is 200,000 tokens (500,000 on Enterprise), against 1 million via the API. And Claude reads text and images, not video or audio.

3. Gemini: 3.8 Flash and deep inside Google Workspace

Google calls Gemini 3.8 Flash, released on 2 September 2026, “our most intelligent workhorse model” (Google, September 2026). If you have Google AI Pro or Ultra, you get it in the Gemini app, in AI Mode in Google Search and in Gemini in Google Sheets. At launch, Artificial Analysis called it “the cheapest model at its level of intelligence”, according to The Register.

The Pro model is still Gemini 3.1 Pro, which has carried the Preview label since February (Google DeepMind). On the independent index it now scores lower than 3.8 Flash: 30 against 41 points. Free users get a Flash model and limited access to 3.1 Pro.

Its biggest strength is integration. Gemini is part of the Google Workspace plans, and from Starter up you get the AI assistant in Gmail and the Gemini app (Workspace). A separate “Gemini Business” subscription no longer exists. Gemini also reads text, images, video, audio and PDF, with a context window of 1 million tokens in Google AI Pro. For going through recordings and long documents, that is a real difference from Claude.

4. Perplexity: search with sources, on other companies’ models

Perplexity does not build a top model of its own. It combines its own model, Sonar 2, with models from others. In Pro you choose from, among others, GPT-5.6 Terra, Claude Sonnet 5 and a Gemini Flash model; Max adds GPT-5.6 Sol and Claude Opus 5 (Perplexity). If you search for free, you get the automatic “Best” mode and a limited number of Pro searches.

The Comet browser has been free since 2 October 2025 (Perplexity), and since March 2026, according to Perplexity, Pro users also have access to Perplexity Computer, Perplexity’s agent system (changelog). How Comet compares to Anthropic’s browser extension is covered in Claude in Chrome explained. For the day-to-day approach per tool, see our practical guide to ChatGPT, Claude and Perplexity.

5. Grok: the outsider with 500,000 tokens of context

xAI released Grok 4.5 on 8 July 2026 and Grok 4.6 on 12 August, both with a context window of 500,000 tokens (xAI). Via the API, Grok 4.5 costs US$2 per million input tokens and US$6 per million output tokens, as long as your prompt stays under 200,000 tokens (xAI). On the independent index, Grok 4.6 scores 44 points and Grok 4.5 39, below the top models from Anthropic and OpenAI.

What do the benchmarks say about ChatGPT, Claude and Gemini?

On the Artificial Analysis Intelligence Index v4.3 of 7 September 2026, Claude Fable 5.1 and GPT-6 Astra share the top with 53 points, followed by Claude Opus 5 with 51. Gemini 3.8 Flash scores 41 and Gemini 3.1 Pro Preview 30. On LMArena, where users compare answers blind, Claude Fable 5 is in first place (Artificial Analysis, LMArena).

Each model shows the best-scoring variant listed on each platform. Artificial Analysis works with points out of 100, not percentages. The same number of points does not cost the same either, as Artificial Analysis itself writes:

“Similar Intelligence Index scores can come at very different costs. GPT-6 Astra (max) and Claude Fable 5.1 (max with fallback) both score 53, but their average cost per Intelligence Index task is $3.26 and $7.63 respectively - 57% lower for Astra.”

— Artificial Analysis, September 2026

Read those figures with some caution. The index changed version twice in one week, so never compare scores from different versions. The makers each publish their own benchmarks with their own test setups: OpenAI reports 99.9% on ARC-AGI-3 with its own harness, while according to Simon Willison it was 62.7% with the standard setup. And on LMArena the newest models still have few votes, so their position may still shift. A benchmark measures how a language model scores on a fixed set of tasks; how it does your tasks is best tested yourself, with good prompts.

Which tool suits your team depends on your own work. ClickForest helps Flemish SMEs in Mechelen and Antwerp with AI training for the whole team.

What do ChatGPT Plus, Claude Pro, Google AI Pro and Perplexity Pro cost?

For one user in Belgium you pay €23 per month for ChatGPT Plus, €18 for Claude Pro (monthly, excluding VAT, or €15 when billed annually), €21.99 for Google AI Pro and US$17 for Perplexity Pro when billed annually. It can be cheaper too: Google AI Plus costs €4.99 and ChatGPT Go €8. All four have a free version.

These are monthly prices as shown from Belgium on 12 September 2026 (ChatGPT, Claude, Gemini, Workspace, Perplexity). Anthropic states that VAT is not included, OpenAI and Google do not say, and Perplexity only shows dollars. For Workspace these are regular prices; temporary discounts vary.

What you get for that money differs too:

• GPT-6 Astra is in the chat from ChatGPT Pro and in Business; Plus only gets it in ChatGPT Work and Codex.
• You use Claude Fable 5.1 on Max and Enterprise, and on Pro only through extra credits; Opus 5 is in Pro and Max, not in Free.
• You get Gemini 3.8 Flash from Google AI Pro, and AI Ultra adds Deep Think.
• In Perplexity you only choose GPT-5.6 Sol and Claude Opus 5 from Max.

A comparison of the features of ChatGPT, Claude and Perplexity per plan is in our AI tools comparison.

Which AI works best with Google Workspace or Microsoft 365?

In Google Workspace that is Gemini: from the Starter plan at €6.80 per user you get Gemini in Gmail and the Gemini app. In Microsoft 365 you work with Copilot, where since late July Microsoft also offers Claude Opus 5 in Word, Excel, PowerPoint and Chat, and since September GPT-6 Astra in Copilot Cowork and Copilot Studio.

That Microsoft rollout can differ by region and by tenant. Microsoft itself adds: “Availability may vary by region and tenant configuration” (Microsoft, July 2026). For Astra, Microsoft followed on 4 September, in Copilot Cowork and Copilot Studio (Microsoft, September 2026). So check with your IT partner what is already switched on in your environment.

For Workspace customers, privacy counts too. Google writes that your content “is not human reviewed or otherwise used for Generative AI model training outside your domain without permission” (Google Workspace). If your team uses neither suite, a standalone subscription to ChatGPT or Claude is often simpler than adding a full office suite.

Do ChatGPT, Claude, Gemini and Perplexity use your data for training?

On the consumer plans they do by default, unless you switch it off: that applies to ChatGPT Free, Go, Plus and Pro, to Claude Free, Pro and Max and to Perplexity Free, Pro and Max. Google uses chats from personal accounts to improve its models. On the business plans, none of the four trains on your business data by default.

That is how it is stated on the pricing pages of OpenAI and Anthropic, in the Gemini app privacy notice, at Google Workspace and on Perplexity’s data page.

The practical rule: do not put personal data or confidential business information into a consumer plan, and take a business plan as soon as your team works with customer data. For customers’ personal data, the GDPR applies as well.

Claude, ChatGPT and Gemini are officially available in Belgium (Anthropic, Google), Gemini also in Dutch and French, and OpenAI confirms GPT-5.6 for the whole EEA (OpenAI). From Belgium, Perplexity simply shows its plans, in dollars. Claude Mythos 5.1 is the exception: for now only for a limited group of US organisations. Under the EU AI Act, Anthropic adds a watermark to output from models released after 2 August 2026; a detection API is still in private preview (Anthropic).

And apart from privacy: no model is free of hallucinations. Always have figures, quotes and legal content checked by a person.

How do Belgian businesses use ChatGPT, Claude, Gemini and Perplexity together?

By using each tool where it is strongest: Perplexity for external research with sources, Gemini for your own files in Workspace, and Claude or ChatGPT for writing, analysing and building. According to Stanford’s AI Index Report 2026, 88% of organisations now use AI (Stanford HAI). At ClickForest we see the difference mainly in how you combine the tools.

This is how we combine the tools at ClickForest in marketing work. How AI fits into your marketing more broadly is covered in the AI marketing guide and in our piece on AI agents in marketing.

1. Market research: Perplexity and Gemini

Ask Perplexity for an overview of your five biggest competitors in Belgium, with their offer and prices, and you get a table with sources. Then put that in Gemini next to your own sales figures in Google Sheets and ask where you are leaving margin on the table. That way you combine current market information with your own data, without copying that data into an extra tool.

2. Content and campaigns: Claude or ChatGPT, with Gemini

Let Gemini analyse the visuals of your best-performing ads, and give that analysis to Claude or ChatGPT to write ten variants of your ad copy. Test the variants, keep what works and turn the rest into content for social media. For larger volumes, ClickForest builds this out into AI content production.

3. Shopify webshop: Claude and Gemini

Export your orders as a CSV and let Claude analyse which products are often bought together. Then let Claude write the code to offer those products as a bundle, and Gemini the product copy in your brand’s tone. Need help with the technical side of your Shopify webshop or with conversion optimisation? ClickForest can help with that.

4. SEO and GEO: Perplexity and Gemini

Use Perplexity to see which questions people ask about your niche and which sources AI answers cite. Then let Gemini or Claude build content based on your own expertise that answers those questions. How you yourself end up in the answers of ChatGPT, Claude, Gemini and Perplexity is the domain of GEO.

Conclusion: which AI should you choose?

After the September releases, Claude Fable 5.1 and GPT-6 Astra share first place on the independent index, and Gemini 3.8 Flash costs only a fraction of both via the API. For one user, the standard plan costs €18 for Claude Pro (excluding VAT), €21.99 for Google AI Pro and €23 for ChatGPT Plus; Perplexity Pro costs US$17 when billed annually.

Our advice: choose first on your software and your tasks, and only then on the ranking. If you work in Google Workspace, start with Gemini. If you work in Microsoft 365, check which models Copilot already offers you. If you do a lot of research, add Perplexity. If you want AI to finish work on its own, Claude with Cowork and Claude in Chrome is a good place to start. And only put personal data in a business plan.

ClickForest helps Flemish SMEs and scale-ups in Mechelen, Antwerp and beyond make that choice and build the tools into their work, with AI training, AI agents and building with AI. Want to talk through your situation? Get in touch.