You may be missing three other programs that are at least as good, if not better (for different reasons) than two and definitely better than one that you mentioned. I am speaking of UNC-Chapel Hill, Greenville, and Wake Forest.
As far as the ones that you mentioned, I interviewed at two of them, so I can comment there:
Duke: Highly academic, plenty of high powered staff, big cases, etc, etc. Too many fellows for me, not enough normal everyday trauma, but good if you want to do research and be a program chair.
USC: Least impressive program out of twelve I visited. Very odd chairman that creeped me out all day, residents that didn't seem happy to be there, bad city, etc. etc. Chilidipper is right that they have some great staff, nice people, but overall not a great experience. All the rumors were quite true for me.
MUSC: Been told by people that they don't think that it would be as highly thought of if it wasn't in Charleston, but then again, didn't interview there, and love Charleston.
Of the others, some quick notes:
Wake Forest: Plenty of trauma, good sports, nice town, nice faculty, residents are happy, kinda higher on the academic side. No real downers that I saw, except the six year track.
Greenville: Great location, very happy residents, community program with perks, good fellowships, friendly attendings/chair. Also no noted downers.
CMC: CMC and Greenville seemed very very similar, almost like brother programs. CMC's chair was a little different also, but no significant downers.
UNC-CH: College town, but can't afford to buy there, the staff was nice, but in a big flux over the past year. Nice facilities, good group of residents, plenty of trauma with wake-med thing, get to make fun of Dukies often.