I will admit that I found your mentioning snow at WUSTL as humorous. I am originally from Montreal and live in the Northeast of the US so we get quite a bit of snow up here. I would be happy to send you some, but am concerned that it might melt before it gets to you.
Would you need to take on any debt at all to attend any of these universities? Would the extra cost of USC and WUSTL be a strain on your family? Would you have “college money in the bank” for medical school if you attend UT Austin? Being $100,000 less expensive over four years seems like quite a difference, particularly since UT Austin is such a good university and since medical school is so expensive.
I would expect premed classes to be very competitive at any of these very good universities. I also would expect you to find premed classes filled with academically driven students at any of these universities. From an academic point of view I think that all three of these are very good. Neither of my daughters were premed, but both had majors that overlapped quite a bit with premed classes and therefore were in many of the same classes. You definitely will want to show up at university ready to work hard from day 1.
In terms of getting accepted to a “top 5” medical school I sort of have two thoughts. One is that there are a lot of very good medical schools in the US, and admissions will be tough at any of them. You do not need to get into at top 5 MD program to do very well with a medical career. My other thought is that you do not need to attend a “top 50” university to get into a top 5 medical school. You do however need strong grades, strong references, and very good experience in a medical environment. As I said neither daughter was premed, but one is currently studying in a top 5 DVM program, and she attended an undergraduate university that was somewhat lower ranked than any of the universities that you are considering.
These are all very good universities. My inclination would be to save the $100,000 and go with UT Austin.
Congratulations on having earned admissions to all three of them. Do not forget that a top high school student can become suddenly average the day that they show up to study at a very strong university (including any of the ones you have mentioned in this thread) and you need to be ready to study at a high level.