There are a few reasons that come to mind, such as winning larger pots on average, and also playing more hands by virtue of not getting knocked out as frequently.
I didn't incorporate any open weights/source models just to limit the number of API providers I had to juggle, but it is just a config change if somebody wants to try a run with them.
I've seen some theories tossed around but I don't think I'm qualified to offer an authoritative answer. Gemini 3 Pro specifically seems to be consistently "tighter" and more passive than Flash.
It greatly depends on the models. The 6-handed setup with Opus and Pro cost about $30/game. The 4-handed setup with just small models was $6/game. I'd love to run more but I already spent quite a bit as it is.