I often read opinions where people say their particular method of more hands-on working with AI is the most efficient and reasonable way.

From 500 hours working on my mobile app project outside of work, I can confidently say that using anywhere between 2 to 10 conversations to parallelize work is much more effective in my project.

The models being served in the API are the same as via the subscription, there are no shenanigans here, particularly not concerning quality.

And GPT 5.5 was great at the time, I made heavy use of it for my project, but it's long outdated and already being retired.

You also mentioned using it in copilot, which is a third-rate harness that is frustratingly buggy and inefficient.

There's no comparison to Opus 5.5 in Claude Code.

Use whatever works for you, but frankly, I think you should try something new.