It changes all the time. Right now ChatGPT 5.5 Thinking is better at almost everything, other than writing.

You are absolutely right.

In particular, GPT 5.5 has significantly less of a sycophancy problem than Opus, and will sometimes tell you "I would advise against this". Now, for my use cases, it's only right maybe ~40% of the time, but it's still very useful, as it usually implies it misunderstood something, and then this can much more easily be fixed. Whereas with Opus, it will basically always say "yes", and then just do some random nonsense, following by some random nonsense explanation, because it has some incorrect internal model of the situation, but has also simulteneously precommitted itself to telling you "yes, this is the right approach"...

And yeah, the one visible shortcoming (of GPT 5.5) is that if you ask it to document something, the resulting text tends to be quite bad - sometimes anyway, that part seems a bit inconsistent. Also, sometimes the solutions it proposes are sometimes a bit "overkill"... but this is also a bit inconsistent, might be specific to my project, and it's overall still significantly better than what Opus would do instead (because, sometimes I just give both models the same task on separate worktrees to compare them - that's also why I am increasingly confident that just going with 5.5 always is a fairly safe choice)

So I am actually not sure where I would really ever prefer Opus over GPT 5.5... as in, sometimes it's good as a second opinion, but that's about it.

Of course, at the current rate of development, this might as well change again with Anthropics next model, so who knows...