As ususal, the reference design seems to be the best, and in that case, get one of the reference based boards. The major differences will be warranty and after sales support. EVGA are pretty good in this respect, and, from experience, XFX are most certainly not.
My 680i is bfg, and if BFG did a 780i, my money would go there (although i am waiting 790i) But if not, i rather like EVGA, especially when they told everyone that they could send their 680i's back and get a new revision board free of charge (well, have to pay p+p)