I interviewed at both.
If you are really interested in one of the two, obviously you should go to that one, but you should also know some stats:
U of SC sent out 100 invitations for an interview, about 80 came. They take 2. MUSC brought in about 26 for interviews (assume slightly more offers), they take 3 although this year they were taking 4 (next year's match will be 2 five yrs and 1 six yr research spot).
So, its tougher to get an MUSC interview but you have better odds of matching: 3 out of about 30 vs. U of SC is easier to get an interview but 2 out of 80 match.
During the interviews at MUSC, they told us to get an interview you need three things if you aren't a student or rotator: >225 Step I AND AOA AND at least one publication. (This may vary slightly based on some outstanding letter from someone who knows someone but that's rare).
U of SC you do have to go away for two rotations, one to Greenville to the Shrine for 6 mo. and one to Augusta to the military base for a spine rotation. Nice private program, best benefits of almost any Southern program, had some trouble about three years ago with some residents not happy with their chiefs and as such this came across to applicants. They also had faculty trouble about 8-10 years ago and have been rebuilding over the last ten years. As a result they didn't fill their two spots a few years ago but you shouldn't worry about that any more as they have turned things around.
MUSC is a nice program in a beautiful location although housing is a little more expensive than most other medium sized southern cities. Small trauma service, chairman has both fans and haters out there, looking for new hand surgeon, hiring a sports surgeon, and the two bastions of peds there are both retiring over next two years so they will also be hiring two new peds people. By the time you got there, all that would be sorted out. Everyone there of course likes it, it seems like everyone has a boat, and they are not as busy as some big city programs.
May or not help, but that's some info for you. I would look at where you think you might want to be between the two as your stock would go up if you do a good job during your rotation. With AVG numbers, you may not get an interview at MUSC, so you might need to rotate there if you are really interested. You may stand a better shot at getting an interview at USC, especially if you have a letter from someone at MUSC that U of SC might recognize and appreciate.