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.