The two models are within striking distance on raw intelligence — the practical choice usually comes down to shape of work, not benchmarks. Claude's instruction-following discipline and tool-use reliability make it the default for anything that has to behave the same way twice in production. ChatGPT's ecosystem (custom GPTs, broad plugin support, image + voice in one product, the cheapest small-model lane) makes it the default for consumer apps where breadth wins.
Pricing is comparable at the workhorse tiers. Claude Sonnet 4.6 is $3 / $15 per MTok; GPT-5.5 is $5 / $30. Claude Haiku 4.5 ($1 / $5) competes head-on with GPT-5.4 Mini ($0.40 / $1.60) — Mini is cheaper, Haiku is more capable. Use the LLM cost calculator to model your actual workload before deciding.
If you're a developer team building agents, internal tools, or code-heavy apps — start with Claude. If you're a consumer brand or you need the breadth of OpenAI's adjacent tooling — start with ChatGPT. Either way, build on the API from day one; consumer apps and the API are different products.