I run 16 PowerColor AX7950 3GBD5-2DHV4 7950's
I also have run another 4 SAPPHIRE 100352-4L Radeon 7950's
I picked up the PowerColors because at the time of purchase they were the only card available in that quantity. I can happily say however I didn't have a single DOA or sub-par functioning card out of the whole lot.
The Sapphires were for my first mining/gaming rig and didn't have a DOA with them either.
In a direct head to head comparison with identical cgminer settings(ran off the same batch file in the same rig actually), the cards average the following:
Temps: Sapphire 71C / Powercolor 79C
KH/S: Sapphire 595 / Powercolor 625
All card have the same settings in MSI Afterburner @ 1025/1500, 1035mv, Powertune +20.
The Sapphires definitely run cooler. Substantially cooler actually. But are MUCH louder. The also were about 20 kh/s short of what the Powercolors topped out at. Not a big deal for a single card, but almost hits 100 kh/s less per 4 card rig. I have them all in identical rigs: Open air case, 990fxa-GD65, Athlon II x4, single 8gb stick, 1200W seasonic.
If I were to purchase again however, I would get the Sapphires for no other reason than the temps. Unfortunately newegg had a 2 card limit at the time of purchase.