I think these are all great opportunities.
HMS: You would go here if you are dead set on doing something outside of clinical/academic medicine or biotech. Say you want to be a politician or entrepreneur that is more public facing. You should also go here if you think 100 K of debt is worth it to be close to home. I wouldn't fault you if you went to HMS for that price tag to be near family. I have a lot of friends at HMS and the student culture is more "conservative" than the student culture at UCSF.
NYU: You should go here if you are trying to expedite your training. It is refreshing to see NYU do this 3 year program. The recent trend in medicine has been to prolong training - gap years before medical school, research year during medical school, chief/research years during residency, extra fellowships after residency. It is starting to get ridiculous and people are not getting their first attending job well into their mid to late 30s sometimes (sorry that was a little bit of a rant).
UCSF: Choose UCSF if you are debt averse but want a more traditional 4 year experience. The stipend is enough from what my classmates with Full COA have told me to cover them so far. The student body here is more liberal and driven to address social justice issues (not that there aren't these types of students at HMS but the culture is more pervasive here). I don't know if this was what you were referring to about not vibing with the students at UCSF but those are my insights into how the two student bodies differ. Also, don't read much into the West coast bias of matching at UCSF, you already know that 70% of the students are from California so its natural that many want to stay in the state after. Plus 1/3 of the class matches back to UCSF (which isn't a bad problem considering like Harvard, UCSF some of the best residencies in the country). Most OOS students can match back to great programs in their home regions from UCSF.
Some other thoughts that went into my decision making in the past:
You've stated you already have connections at HMS. That is great, but do you think you could grow your network more if you left Boston and made connections at another institution (NYU or UCSF)? Do you value gaining a different perspective on life and culture to working in medicine (more likely to get that at UCSF)?
Just to reiterate, you can't go wrong with these schools. HMS really only beats these schools out on layman prestige and proximity to family. Is that worth 100K of debt for you? Only you can answer that. If you are planning on doing clinical/academic medicine, you should view UCSF and NYU as peers of HMS and not take into account the layman prestige. Congrats on these great options.