Tough choice. Free is pretty darn attractive. How much can your folks afford to pay for college? Med school? Would you be wiling to join the military or some other sort of special program to help pay for med school?
Finances could be the deciding factor here, I am sorry to say.
If it doesn’t come down to $, I’d go with UT. The whole UT experience would be richer than the UT Dallas experience. It would also be tougher, however. (This is hearsay) UT Dallas might be easier for a pre med, and may have better pre med advising. You would be well prepared for the MCATs at either school.