GPT-6.1 vs Claude 5.5 vs Gemini 4
Published 2026-10-18 · Updated 2026-10-26
The frontier right now is a three-way race between OpenAI’s GPT-6.1 line, Anthropic’s Claude 5.5 family, and Google’s Gemini 4. Benchmarks shift monthly; the durable differences are these.
GPT-6.1 (OpenAI)
- Strength: the most predictable all-rounder. Strong tool use, the largest third-party ecosystem, and the
sk-proj-project-key model that makes key management granular. - Weakness: flagship pricing is the steepest of the three; the mini tier carries most of the value for everyday work.
- Choose it when: you need maximum compatibility, every tool, SDK and tutorial assumes OpenAI-shaped APIs first.
Claude 5.5 (Anthropic)
- Strength: coding and long-document work. Anthropic has leaned hard into agentic coding, and it shows in multi-step tool chains and repo-scale editing. The
sk-ant-api03-keys and the distinct API shape are the tax you pay for it. - Weakness:
max_tokensis mandatory, the native API isn’t OpenAI-compatible, and context handling behaves differently enough that code tuned for GPT needs real porting. - Choose it when: the workload is code, agents, or careful long-form writing. It’s also the default inside most serious coding tools.
Gemini 4 (Google)
- Strength: context window and price. Google’s million-plus token contexts with competitive per-token pricing make it the answer for “shove the whole codebase in” tasks. AI Studio’s free tier is the most usable free tier of the three.
- Weakness: API ergonomics, key-in-URL on the native endpoint, an OpenAI-compat layer that lags the native features, and stricter region/safety behavior.
- Choose it when: you need huge context, cheap multimodal, or a genuinely free tier for prototyping.
The honest shortcut
All three are on OpenRouter. If you’re not sure, take an OpenRouter key, run your ten hardest prompts through all three models, and pick on your own outputs rather than a leaderboard. Provider benchmarks measure their benchmarks; your prompts are the only eval that matters.