Comment by code_biologist

My use case is mostly creative writing.

IMO 2.5 Pro 03-25 was insanely good. I suspect it was also very expensive to run. The 05-06 release was a huge regression in quality, most people saying it was a better coder and a worse writer. They tested a few different variants and some were less bad then others, but overall it was painful to lose access to such a good model. The just released 06-05 version seems to be uniformly better than 05-06, with far fewer "wow this thing is dumb as a rock" failure modes, but it still is not as strong as the 03-25 release.

Entirely anecdotally, 06-05 seems to exactly ride the line of "good enough to be the best, but no better than that" presumably to save costs versus the OG 03-25.

In addition, Google is doing something notably different between what you get on AI Studio versus the Gemini site/app. Maybe a different system prompt. There have been a lot of anecdotal comparisons on /r/bard and I do think the AI Studio version is better.