Best UC for Psychology major?

It depends on what you want to study.

If you go by US News, it’s UCB and then UCLA, both top 5.

If you go by Niche, it’s UCLA very high and then UCSD #19. Then Irvine, then Berkeley.

If you go by College Factual, it’s UCLA and then Irvine - although neither is high.

Psych is the kind of degree you can do well with from anywhere - but some schools might have wider course offerings than other.

Good luck.