I'm deciding which to buy, heres a link to the specs:
XFX:
http://www.scan.co.uk/Products/1GB-XFX-HD5770-PCI-E-20%28x16%29-4800MHz-GDDR5-GPU-850MHz-Cores-800-2x-DL-DVI-I-HDMI
Sapphire:
http://www.scan.co.uk/Products/1GB-Sapphire-HD5770-PCI-E-20%28x16%29-4800MHz-GDDR5-GPU-850MHz-Cores-800-2x-DL-DVI-I-HDMI
XFX:
http://www.scan.co.uk/Products/1GB-XFX-HD5770-PCI-E-20%28x16%29-4800MHz-GDDR5-GPU-850MHz-Cores-800-2x-DL-DVI-I-HDMI
Sapphire:
http://www.scan.co.uk/Products/1GB-Sapphire-HD5770-PCI-E-20%28x16%29-4800MHz-GDDR5-GPU-850MHz-Cores-800-2x-DL-DVI-I-HDMI