I don't typically use a ton of vinegar in my sauces so I use a jug of cider vinegar, rather than wasting a better bottle in something where it will be overshadowed.
I do some comps so take this as comp advice, but it kind of goes along with bbq in general. A KC style sauce (IMO) should be fairly neutral, or familiar. When making my sauce, I use Hienz ketchup, French's mustard, etc, because it gives me a flavor that I think everybody can relate too.
Of course, I do have a pantry of vinegar (my wife kind of collects them) and I highly recommend seeking out finer vinegar because they have their place in any kitchen. I don't usually use flavored vinegars but I look for small bottles of better wine vinegars, because (IMO) the stuff sold as red wine vinegar at the supermarket can not be made from actual wine.