For thinking through decisions, Claude Pro ($20 a month, or $17 billed annually) is the strongest of the four in October 2026: it includes Claude Opus 5.5, top of the Artificial Analysis index at 58 points, with up to a 1M-token context. Measured against Daniel Kahneman's outside-view test, pair it with Perplexity Pro for sourced base rates. ChatGPT Plus remains the best all-rounder.
"Which AI is smartest?" is the question most comparison pages answer, and for decision work it is the wrong one. A month of releases (Claude Opus 5.5 on September 22, Sonnet 5.5 on September 28, GPT-6 Sol arriving in ChatGPT's regular chat from October 7) has reshuffled what each $20 plan actually gives you, so the question is worth asking again with a better yardstick.
The yardstick comes from Daniel Kahneman's Thinking, Fast and Slow. Kahneman's decision errors cluster in three places: WYSIATI ("what you see is all there is"), where we build a confident story from whatever is in front of us; neglect of the outside view, where we ignore base rates for situations like ours; and overconfidence, which grows with the coherence of the story rather than the quality of the evidence. A subscription cannot cure those, but it can make the cure cheaper. So I compared the four plans on three things: can it hold the whole decision file (context), can it fetch sourced base rates (outside view), and how strong is the reasoning model you get at this price (the closest thing to a tireless System 2). The table is built from the vendors' pages and an October 3 comparison by ClickForest; it is a reading of documented features, not a benchmark I ran.
| Plan (price, checked October 9, 2026) | Strongest chat model at this price | Whole file | Outside view | Kahneman verdict |
|---|---|---|---|---|
| Claude Pro ($20/mo, $17/mo billed annually) | Claude Opus 5.5, 58 on the Artificial Analysis index; Fable 5.1 only through usage credits | Up to 1M tokens | Web search and Research built in | Best System 2 partner for a premortem |
| ChatGPT Plus ($20/mo) | GPT-6 Sol in Chat since October 7; GPT-6.1 Sol (52) in Work and Codex | 54,000 tokens for instant answers, 256,000 with Thinking | Deep research and a built-in browser | Best all-rounder; check how much of your file it really holds |
| Google AI Pro (€21.99/mo in the EU) | Gemini 3.8 Flash (41); Gemini 3.1 Pro is still a preview (30) | 1M tokens, and it reads video, audio and PDF | Deep Research; Gemini inside Gmail and Docs | Best when the evidence lives in Drive and recordings |
| Perplexity Pro ($17/mo billed annually) | No model of its own: Sonar 2 plus others' models (its September 4 list: GPT-5.6 Terra, Claude Sonnet 5, a Gemini Flash) | Not the point of the product | Strongest: every answer cited; Perplexity Computer now on Pro | Best base-rate finder, weakest sole thinking partner |
The verdict follows from the columns. Claude Pro is the best single plan for decision work in October 2026 because it combines the highest-scoring model of the four with a context window large enough to hold the board deck, the customer interviews and last quarter's numbers at once, which is the practical answer to WYSIATI: the model can only question what you give it. ChatGPT Plus is the better tool if your week is mostly varied tasks and you want one app; its move to GPT-6 Sol in regular chat narrows the gap, and OpenAI did not change any prices with that rollout. Google AI Pro earns its place only if your company already runs on Workspace or your evidence is meetings and video; its strongest model available today scores well below the other two. Perplexity Pro is the odd one out and the most Kahneman-shaped: the outside view is a question of base rates ("how often do companies like mine succeed at this?"), and a cited answer you can open is worth more there than a fluent one.
If I had $37 a month for decision work, I would buy Claude Pro plus Perplexity Pro and split the job: Perplexity for "what usually happens in situations like this, with sources," Claude for the premortem ("it is a year from now and this decision failed; write the history"). If I had nothing, Claude's free tier now runs Sonnet 5.5, which scores 56 on the same index, ahead of every model with a published index score in the ChatGPT Plus and Google AI Pro rows above.
The limits matter. Index points are not your decisions, and Anthropic itself wrote at the Opus 5.5 launch that benchmark margins "have become a less reliable guide to real-world differences." GPT-6 Sol in regular chat has no separate index score yet, so its row leans on GPT-6.1 Sol. Perplexity's model list dates from September 4 and its own help pages say the selector in your account is the only reliable reference. Prices differ by region and tax. And no plan fixes the deepest Kahneman problem, which is that a model will help you build a more coherent story for the choice you already wanted. You have to ask it to argue the other side, every time.
Sources: Claude plans and pricing, Anthropic, checked October 9, 2026; Claude vs ChatGPT vs Gemini vs Perplexity: which AI model to choose in 2026?, ClickForest, October 3, 2026; ChatGPT Go vs Plus vs Pro: which plan should you pay for?, The AI Career Lab, reviewed October 7, 2026; Google AI Plus, Pro and Ultra plans, Google, checked October 9, 2026; Perplexity release notes, October 2026, Releasebot; Introducing Claude Opus 5.5, Anthropic, September 22, 2026; ChatGPT Context Window and Token Limits by Plan (2026), AI Toolbox, updated September 15, 2026.
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