I'm from Califonia, very near Davis, but I have been living in Dallas and working at UTSW all year. Personally, I would go to UCDavis ovre UTSW in a heartbeat based on locatio nalone, but being from SoCal you might appreciate Dallas more than me. Do you like going to restaurants, going to bars, going to malls, and going to some more restaurants? Come to UTSW! Do you like doing... anything else? Do you like seeing or at least being close to mountains and water of ANY kind? Do you appreciate wildlife (beyond thousands of grackles)? Try UCDavis. Seriously, I have enjoyed it here more than I expected to- the people are very friendly and fun, there are great museums and....malls.... and restaurants- but I wouldn't want to stay much longer.
As for the schools: FWIW, here are the impressions I have gotten about UTSW while working here (bear in mind I never considered it for school so I haven delved too deeply): UTSW is a great school whose students work very hard and perform very well. I have also heard from a few student who did away rotations (UTMB) during 4th year that they felt very prepared and like expectations here are higher for the students. As for negatives: I have gotten the feeling that things here are more prescribed, less diverse- this refers to the students, their experiences, and their opportunities during med school. A little cookie-cutter, perhaps. I also have talked to one UTSW gen surg resident who came from another med school and thought that the resident who come from UTSW are "coddled"- less exposed to and prepared for the real world of medicine. That's just one person's opinion, though.
As for UCDavis, you probably have a better sense of the school than I do, having interviewed and whatnot. Great school, great combination of focus on researhc and primary care experience, great clinical training and opporunities to work in free clinics, etc. I cannot speak to the new facilities in Sacramento personally, but a friend whose dad works there says they are fantastic and that the students are very pleased.
Since you have two good choices, you should go to the place where you feel most welcome and comfortable. You should feel just plain happy with the school and the student body- and yes, the surrounding area matters too. It is your life and you want be in an environment that is a good fit for you for the next four years. Good luck! 🙂