Georgey was right about getting grief for bashing STL. My family has lived here for about 12 years. I went to undergrad out of state am back in St. Louis working at WUSM as a research assistant. I am applying to med school and if accepted to WU, I'd attend in a second.
I've never been to Austin, so I can't give comparisons. However, I can tell you a little bit about what St. Louis has to offer: diversity-a city on the MS River STL was hub for immigrants and their communities and neighborhoods thrive today, festivals galore (2nd largest Mardi Gras parade and celebration, awesome St. Patty's Day Parade) great clubs and bars, shopping, restaurants, sports (The Blues, Cards, Rams), theatre, city fun without the high prices, easy to be in the city or get away from it all, very friendly people. Yes, there are a few less desirable things about STL. The summers are REALLY hot and humid, winters not that bad, spring and fall are beautiful. Also, even though the public treansportaion is improving, you really do need a car to get around town. As for WUSM itself...awesome, endless number of opportunities (clinical and research based). If you get an interview, come and check it out for yourself. You might love it. Good luck!