This all comes down to personal experience i guess but i can tell you that i have had plenty of cards through my hands over the years and after 2 going wrong in quick succession i wont touch a powercolor card again. I was probably unlucky but thats what i have actually had happen.
XFX have legendary customer service. I have yet to hear a bad word said about either the hardware or the company.
All the rest hav eno real negative points im aware of personally. Sapphire get a bad press on most forums for customer service, EVGA are nearly as good as XFX in my book, MSI, ASUS and GIGABYTE all decent brands i wouldn't hesitate to buy.
Sparkle, Palit and Powercolor not so.
Mactronix