USC is a great music school, Thornton is highly regarded (I don’t know the piano faculty, but I would assume they are high level) and obviously being in the LA region could provide networking and opportunities you might not get through UT.
If you are thinking of using student loans to make up the difference, if your family cannot contribute much, please keep in mind that your assumptions about coming out of school and making a living (in some combination of music and ‘real’ jobs likely) enough to pay rent and food and the debt may be optimistic. It takes a while for a young musician to find their way into making a living, as a pianist you would be competing with a lot of people out there, and with gig work especially that comes about when you establish a network, and that takes time. There are student loan calculators on line, run the numbers for projected debt for either school, that likely will be in the many 10’s of thousands of dollars, and you will find that the payments will be significant. If you hang out in LA after graduation USC, you would also face a pretty high cost of living.
I am not telling you to take either of these opportunities, rather I wanted to point out that getting jobs in music may not be as easy as you think and that even combining day jobs and gigs you can find likely won’t pay as much as you think. The standard line with music school is to take on as little debt as possible, and if you do save that for grad school. These days with music the tendency is kids who graduate with UG degrees going to grad school, so keep that in mind, that on piano especially that is so competitive the MM degree is quite common and becoming more so every day. When looking at your future, be careful to temper your optimism towards being conservative, and also be aware that it may take education/training past the UG level.