They are interchangeable maybe in your case. In my case for my tasks and for my product, Opus and GPT are at a level where I can vibe code with them and trust them, whereas the others aren't really there. When models get better they'll reach whatever point you need to be able to trust them.
But sounds like Opus and GPT are interchangeble for your case.
You said above that "Opus 5.5 still makes a lot of mistakes". This seems to contradict what you are saying here?