I thought I would throw in my 2 cents since I did med school at Davis and am now in path at Stanford.
I really liked Sacramento for a few reasons: affordable place to live, so tons of young single people and young families as opposed to the bay area, and proximity to Tahoe, Napa and SF. Davis is a little more small townish, but has all the undergrads keeping up the nightlife, etc.
I think the program has a lot of positives. The faculty are great, very bright and good teachers. The material is outstanding in terms of variety of bread and butter mixed with the exotic, given that UCDMC is both a county hospital and tertiary care center (referral center for a HUGE geographical area that is growing rapidly).
The one thing about the program is that it is VERY flexible. That can be good and bad depending on who you are. If you are self-disciplined, you can be very successful at Davis.
Given those things, I am suprized Davis does not have a very good reputation, and I'm not sure why that is. Several years ago there were several faculty that were very unhappy there and left for other places. I can't comment any more on that, as it was before my time there.
As to why Davis has the rep it has, it is a long story. There was a time when a very slick MDPhD from UCSF was at the helm, he left for research. Davis has always had a real split campus with half the education in Davis itself, the cllinical part in Sac. From my understanding (and I have relatives who are faculty), the entire med school is being moved to Sac. Bad bad idea if you ask me from a research standpoint but if you are research type med student you are probably setting your sites on Stanford, WashU etc.
All that being said, I think the best way to decide between programs is to do an away rotation. I think all the previous posters have made excellent points. My take on it is that programs are trying to find residents that are "good fits" for their program. Your personality may fit like a glove one place and not at another, no matter how "cool" you are or charming or boring or whatever. Anyway, just my ramling, take what you will...