GPT-5.1 and Claude Sonnet 4.5 are the two models most people should reach for day to day. GPT-5.1 is the warmer GPT-5 refresh, with adaptive reasoning, a more natural tone and better instruction-following, and a great generalist for writing, chat and lightweight reasoning. It sits just below GPT-5.2 in capability and price.
Claude Sonnet 4.5 is the coder's default: clean, well-structured code, careful prose and strong tool use at an attractive price. For pure writing tone, GPT-5.1 is delightful; for coding craft and structured output, Sonnet 4.5 tends to lead. Both are affordable enough to use heavily, and many people keep one of each: GPT-5.1 for conversation, Sonnet for code.
Which should you choose?
GPT-5.1
GPT-5.1 · 400K context
Pick it if
you want warm, natural writing and general assistant work.
Claude Sonnet 4.5
Claude Sonnet 4.5 · 1M context
Pick it if
you want clean coding and structured, careful output.
GPT-5.1 wins on conversational tone and general writing; Claude Sonnet 4.5 wins on coding craft and structured output. Both are excellent, affordable defaults.
Questions
Which writes better?
GPT-5.1's tone refresh makes it especially pleasant for natural writing; Claude Sonnet 4.5 is excellent too, with a slightly more precise, structured style.
Which is better for code?
Claude Sonnet 4.5 is the developer favourite for clean, reliable code, though GPT-5.1 is a strong coder as well.