Newegg?

Well, here is a breakdown between those 3:

BFG: Lifetime warranty, NO overclocking or you void it; have to buy one of their OC'd cards.
EVGA: Lifetime warranty, OC-FRIENDLY (as long as you don't flash the BIOS or physically damage it), and Step-up. If a faster card comes out (or you just want a GTX 285 real bad because your 260 isn't fast enough), you can Step-Up to that card and only pay the difference.
XFX: Double lifetime warranty (lifetime for you AND the person you sell it to), OC-FRIENDLY (as long as you don't flash the BIOS or physically damage it).

That's about it. But if you don't plan to overclock it (which I highly recommend if you get XFX or EVGA), just get the one with the fastest clocks. But, it should be known, GPU overclocking isn't as effective as say CPU overclocking. A 20% clock increase will almost NEVER net you anything close to a 20% FPS increase; closer to 10% if you're lucky. Happy

~Ibrahim~