I would go with the Coach bag. And NOT just because it's Coach because I am an MK fan as well (not as much as Coach though) but I think the Coach one is prettier. IMO I guess I would have to see the MK one in person but that silver almost makes it look like it's spray painted that color.
Probably MK but I've seen that bag everywhere lately. I like silver better than gold. I've never seen the Coach. If you get that one, I think you are less likely to run into someone else carrying the same bag.