well i guess i depends on the card you are getting... both are amazing brands, but i think you get a lifetime warranty on anything EVGA, and it pretty much covers everything (even if you overclock and it melts )
my 7900gt was like partially fired when i PSU fried back when in my old comp and it still worked after new PSU though it died about a month ago so but that thing was a trooper, 9600gt from them is awesome and it came in a wicked sick box that i was like omg thats awesome imma buy it (no not really)
I've got an XFX 8800 GTS and its never failed me yet. I have a lifetime warranty on it as well. I would probably go with eVGA but my local computer store didn't carry the eVGA 8800. So eVGA is my pick but you wouldn't go wrong with an XFX.
Hardware has been trouble free. When support was needed - usually a dumb question like SMART support when RAID'ing, I'll get an email turn around in a couple hours. Using a eVGA 780i mainboard and 9800gx2 (from a 8800gts).