With any component you buy, there's always a chance that you might get a lemon. Hopefully you won't but if you're really worried about that, just make sure you buy a brand new one, so you can have it replaced if found deffective within the warranty period. That should give you a little peace of mind.
By the way, make sure that you take note of the lenght of both GPUs. The Gigabyte (312mm) one is longer than the EVGA(241.3mm) one. It might not fit your case.