The answer to this is gray. You will find perceived quality differences by owners of cards. Some people are EVGA people, while others swear by XFX. Some think Sapphire is junk, others think it is just as good while being cheaper. It's kind of like asking what is better, a Camry or an Accord.
The warranties are the biggest differences. EVGA and XFX both offer lifetime warranties. I believe EVGA doesn't void their warranty with aftermarket coolers. XFX has less hoops from what I've read.
Personally, I have an EVGA and like it. I'd narrow it down to what model card you want (ie 9800 GT, GTX 260) and then read reviews on the different brands. of each model. Then post a couple here, and people will help you make a good choice.