Another difference: stack overflow tells you you are wrong or tells you and do your own research or to read the manual (which in a high percentage of cases is the right answer). It doesn't tell you that you are right and proceeds to hallucinate some non-existent flags for some command invocation.
It mostly incorrectly flags your question as a dup.
This is a problem but it's a known one which both Google and Anthropic seem to be making progress towards solving. I've had a full on argument with Gemini 3 where it turned out I was wrong and it correctly stuck to its guns and wouldn't let me convince it otherwise. It eventually got through to me about the mistake I made and I learned something useful from it. Sonnet and Opus are still a bit too happy to tell you "you're absolutely right" but I've noticed more pushback creeping in in the right places. It's a tough balance to get right, nobody wants to pay for a service that just tells them "no" whenever they want to try something silly or unconventional.