Re: Charleston, Columbia or Greenville?
1) Columbia - home to my alma mater, THE University of South Carolina. An often underrated city that offers a great deal of options, whether it be outdoors activities (kayaking / tubing the river, Lake Murray, Harbison Forest, Congaree National Park), shopping, dining, arts, music (improving), sports (USC, of course, but also potential for future minor league team). Plus, Columbia has easy access to most areas of the state. Try living in Greenville and getting to the beach- considerably longer drive.
2) Charleston - Sorry, spareparts...even with the influx of Ohioans (go back!!!) Charleston is still a great place to be. Multiple beaches (I'm partial to Folly), history, great dining, shopping, music, arts...it has it all. Well, everything except USC and easy access to other parts of the state...
3) Greenville - Putting it #3 seems like a slight, but it's only by default, simply because I think that highly of the cities above it. Greenville is a thriving Southern city with a wonderful downtown area and a growing economy.