I think Cosmic's Ray's has the best. There is so much to choose from that my veggie burger always looks like such a mess when I'm done topping it. And then I always think, "Why did I do that?" and then the next trip I do it again.
Pecos Bill's gets my vote! I love that you can add mushrooms, onions, and that horrible for you but yummy "cheese" to your food. I think the one at Cosmic Rays is pretty similar, but it always seems to be so much busier there, that we prefer PB's!