The best brand to get is rather irrelevant, a good retailer will test the card, find it faulty, send a replacement same day from stock, RMA the dud card, get a brand new one in return and put the brand new one in stock for normal sale. AIB's have entirely no problem with that setup, neither do distributor's. I can count on one hand the number of companies who ship repaired parts back for replacements, they are VERY few and VERY far between.
Asus were about the best, we filled out serial numbers of items in a rma form, no other info necessary(to distributor who covered Asus for us), we sent them off and we got brand new stuff back VERY quickly. Company I worked for has sinced gone under though, but a good retailer will pretty much shield you from all RMA woes, they are very few and far between themselves though. a certain very very small, and direct company from up north insisted on waiting to replace my not made any more gigabyte board, and 5 weeks later ended up replacing it with a newer version from stock anyway, which I asked them to do the second they confirmed it was broken.
Needless to say I don't use them anymore, they used to be fantastic though, bought a gf4 ti200 way back, tried it, was completely unimpressed as an upgrade from a gf3, asked if I could return it and buy a 9700pro from them when it was out in a few weeks, they said no problem and held back a 9700pro from the first shipment they had, I had one days after release, and it was freaking awesome. Not as good anymore though
Powercolor barely do anything to the card anyway, at the moment AIB's are basically putting stickers on still, thats about it, everything else is done for them, some 3rd party ones are out and are slightly different, generally still made by the same people to the same quality level.
Most cards will be DOA, the odd one dies in shipping or slips past QA, the massive majority of the rest will die, eventually through overheating, clogged fans and or overly hot rooms and cases. A few will die due to users smegging up, replacing heatsinks, not installed correctly, something along those lines.
ACtually quite a lot die after fans die, which again leads to overheating and long term damage. Asus cards were ruddy awful for that ages ago, their custom 2 fan coolers had horrible fan quality, we got loads of those cards back, x800 era, and both fans were dead.