You spent like a split second with your fellow admits at both schools. I can tell you confidently that it means very little. First, you don't know how many will even end up there lol. Also, class dynamics change constantly during medical school. The same folks who you clicked with during your visits might not actually be the right friend group for you when you start school.
Wrt nightlife, you're really splitting hairs here. And SF has great public transportation so I don't think you'd need a car. Tbh, you really don't have any cons for UCSF. Then add on the fact that it's in the state you wanna settle down in, cheaper, and pass/fail clerkships? This really shouldn't be a question, UCSF easily imo lol