So far, which model can find/solve what is really scattered all over the place.
GPT-5: Exceptional at abstract reasoning, planning and following the intention behind instructions. Concise and intentional. Not great at manipulating text or generating python code.
Gemini 2.5 Pro: Exceptional at manipulating text and python, not great at abstract reasoning. Verbose. Doesn't follow instructions well.
Another thing I've learned is that models work better when they work on code that they themselves generated. It's "in distribution" and more comprehensible to them.
My very first use of the llm-consortium saw me feeding in it's own source code to look for bugs. It surfaced a serious bug which only one out of the three models had spotted. Lots of problems are NP-ish so parallel sampling works really well. Googles IMO gold and openais IOI gold both used parallel reasoning of some sort.