Better code hands down. Actually GPT 5.5 is a good example of a model that's generally better at solving problems than Opus 4.8, but the code it generates is worse - over engineered, shortcuts, etc.. Fable does both, better code and solves problems, but it's also very expensive. Currently I use Opus mostly, Codex for code reviews because it is pedantic, and Fable for tough problems and high level design.
