I am not biased as I will be attending McGovern this year but I interviewed both at UTMB and UTHSA. Personally, I didn't like the feel at UTMB AT ALL. Nothing against the people but I didn't really feel like I meshed with the student body there, everybody seemed so awkward to me. I also wasn't a particular fan of the campus nor the location tbh. I interviewed early August, it was sooo humid - I hated it. My first interview was UTHSA and I also currently live in SA. I loved the atmosphere at the school and all the students I met were so nice and down to earth - not awkward at all. Plus that new building at UTHSA is AWESOME. Lowkey jealous that you'll hopefully be attending lectures there plus there was so many study areas with great views too. San Antonio is a great location to live because you can live close to the med center and not go broke lol - also, I think you would see a lot more at university hospital then you would over in Galveston (just assuming).
Notice I haven't mentioned academics, I feel like they're both slightly similar in that sense except UTHSA seems more holistic to me. UTMB boasts high GPA (one of the highest avg. GPAs in Texas) and MCAT which I think kind of shows in the student body (awkward peeps) but maybe I'm just an ass^%*}. I am biased to SA as well though because ive lived here for 5 years and I LOVE it. I personally had a hard choice choosing between ranking McGovern and UTHSA..
I hope this slightly helps, I was probably just rambling but im at work! Cheers!