But GPT 5.3 Codex is great. Significantly better than Opus, in the TUI coding agent.
But ChatGPT is still SOTA in search and hard problem solving.
GPT-5.2 Pro is the model people are using to solve Erdos problems after all, not Claude or Gemini. The Thinking models are noticeably better if you have difficult problems to work on, which justifies my sub even if I use Claude for everything else. Their Codex models are also much smarter, but also less pleasant to use.
Gemini is really good with many topics. Vastly superior to ChatGPT for agronomy.
You should always use the best model for the job, not just stick to one.