Neither. The 680 is an absolute waste of money - it's only 5% faster than a GTX 670, but it costs 25% more. That means you're paying $100 for about 5 more fps. (And since both cards max games at 1080p and 60Hz, it's not even like those 5 fps make any difference at all.)
I'd get the EVGA 670 FTW. Make sure you get the normal FTW, not the FTW + or LE. The Asus will be slightly cooler, but the EVGA will be faster, is only a dual slot card, and its warranty is freaking amazing. (As in, you can overclock and burn out your card and just return it for RMA.)