To be honest Columbia doesn't hold a candle to Charleston.
The weather sucks, the 'culture' is limited.
However...
There are no hurricanes in Columbia,
Housing is DIRT cheap in Columbia,
USC is part of USC... meaning you can participate in all of the USC activities- football games, intramurals etc.
Getting to the school and getting aroung the school is MUCH easier.
The education at USC and MUSC is the same, students at both schools get an excellent experience and get into their top ranked choices.
Overall... go where you want to be- you are going to get the same education, from the same books, take the same tests whether you go to MUSC or Charleston. If you'd rather spend what little time you have outside of class at the beach go to Charleston, if you'd rather be at the lake go to Columbia.
Good luck,