My experience is that if I know what I want, CC will produce better code, given I specify it correctly. The planning mode is great for this too, as we can "brainstorm" and what I have seen help a lot is if I ask questions about why it did a certain way. Often it'll figure out on its own why that's wrong, but sometimes it requires a bit of course correction.

On the other hand, last time I tried GPT-5 from Cursor, it was so disappointing. It kept getting confused while we were iterating on a plan, and I had to explain to it multiple times that it's thinking about the problem the same way. After a while I gave up, opened a new chat and gave it my own summary of the conversation (with the wrong parts removed) and then it worked fine. Maybe my initial prompt was vague, but it continually seemed to forget course corrections in that chat.

I mostly tend to use them more to save me from typing, rather than asking it to design things. Occasionally we do a more open ended discussion, but those have great variance. It seems to do better with such discussions online than within the coding tool (I've bounced maths/implementation ideas off of while writing shaders on a personal project)