It's been a while since the latest failure rates comparison between assemblers was made, back in the AMD HD 7xxx series I think. There was only one brand worse than Sapphire that isn't even for sale here in Spain. Neither is Powercolor. XFX has also been a cheap, not highly recommended brand.
Anyways, nowadays I've seen many more cases of faulty Sapphire cards in spanish forums, like half of the opened threads about faulty cards are Sapphire cards. I guess this can't be taken as a rule but I am really not confident with this brand.