How good are you at even bindings and neat corners? If you're a stickler for really tidy, precise binding work, then I think the dark fabric would be nice. If you're still learning, or you don't really want to invest the time in making the corners perfect, then I think that you're better off with a match to the border. My observation is that bindings are among the top problem areas where quilts fall into the "loving hands at home" category of crafting. I've learned not to make a showpiece of them unless I really intend to do it right.