They are both good programs. Minneapolis is a great all around city. Charleston is nice too but not as metropolitan. Charleston has great weather all year round, and I recall that some residents even had boats.
Minnessota residents have 3 hospitals they cover, so there is a little driving but not more than 10 minutes or so between each facility (VA and County hospital). The Va and county provide a plethora of volume clinically and surgically. In fact, I believe that UNC sends its senior residents to Minnesota to boost surgical numbers because of the great volume of the Minnesota program.
One of my prior co-residents is currently doing a combined Peds/Plastics fellowship at MUSC while her husband does a Heme/Onc fellowship there. I have heard she is happy with her training there.
When I was interviewing for residency, residents seemed happy at both places. Personally, I liked Minnesota better and think it is the better program...but you wont go wrong either way.