Charlotte, NC: I don't recommend if you're a young single person. Mediocre at best night life, very family oriented, difficult to meet people. On the flip side, you're only three - four hours away from the beach and a couple hours away from the Appalachian Mountains. Cost of living is pretty cheap, especially if you don't live in Uptown, Dilworth, Southend, or Southpark. Traffic isn't too bad but the city is outgrowing some of its existing roads and freeways.
Charleston, SC: Great place to live, awesome night life and there's a ton of bars and restaurants. Isle of Palms and Folly Beach are both nice beaches and great places to hang out. The cost of housing is pretty high but everything else is pretty cheap. Girls will love the shopping on King Street. Traffic sucks and is made worse by all the old people and tourists in town, but if you live and work downtown, you never really have to get in your car.
The weather is pretty good in both places. It can get pretty hot in the summer (mid-to-upper 90's) but you get used to it after a few years. It only snows once or twice a year at the most. Since I've been down here from Michigan (roughly 13 years ago), we've only had heavy snow twice.