In S.C. you can most likely tell what kind of BBQ sauce you'll be eating by looking at the soil you're standing on. I know this may sound strange to folks from other states but it's true.
If you get BBQ in the Low Country where the soil is sandy and loam you are going to get clear vinegar/pepper based sauce. Move up to the Midlands where the soil is orange clay and you'll find my favorite mustard based sauce. Drive up to the Piedmont or upstate where the soil is red clay and you can expect to see ketchup based sauce.
Carolinians, although only separated by a couple hundred miles at most, can get right defensive about their regional sauces. Columbia/Midlands folks don't cotton to that tomato based stuff and the Pee Dee folks look down on anything that ain't vinegar/pepper. I've heard people from the upstate say "you put mustard on hotdogs not BBQ". The Sticky Fingers chain knew they'd never sell their Q in Columbia without introducing their Carolina Gold sauce.
Growing up in the Piedmont, spending time at the beach and living in the Midlands has made me appreciative of all three types.