All of them are great. Reviews are very close. Sapphire rates a bit better. You may want to wait a couple weeks. Nvidia's mighty Titan is coming out perhaps on Feb. 18th or so. Not that your would buy it a $900+ dollars, but it could push AMD's prices down.
The other card i would recommend are Sapphire's HD 7950 Vapor-X comes with a large dual-fan cooler that uses the company's famous vapor-chamber technology. On the Vapor-X you will also find a "Lethal Boost" button which switches to a second BIOS with higher clock speeds. With this BIOS, clocks are increased to 950 MHz GPU and 1250 MHz memory.IMO it's the best 7950.