When you say "Gemini", which exact model do you mean? You know there are several and they vary a lot in how capable they are? Pro 3.1 Preview, 2.5 Pro (their latest non-preview pro model), Flash 3 Preview, ...

Same with GPT-5: Latest 5.5, prior 5.4, or actually the original 5 (.0)?

You can't talk about model performance without specifying the exact model.

My apologies, I thought it would be implicit that I am using the top-tier model of the time given the challenge of the tasks. GPT-5.5 was too new in this top comment (although I did test it a bit in a comment below), so I was using GPT-5.4. Gemini is Pro 3.1 Preview.

High bet on 3.1 pro. I use it a lot for math and classic engineering, it's very strong.