You don't say what nation you are in, but in America the XFX is the better value. It has a 3 year warranty vs. Sapphire's 2-year warranty. Also, currently on NewEgg the XFX card is $200 after a $30 mail in rebate vs. Sapphire being $225 after a $15MIR.
The Sapphire comes out on top having a higher core clock speed: 1342MHz vs. 1288MHz for the XFX. I have not seen any comparisons of these two cards side by side, but based on some user comments, the XFX also seems to have the better cooling solution. Too many reports of the Sapphire running hot under load even when not overclocked.
But the bottom line is this (assuming you are in the US): are the longer peace of mind warranty with XFX and the rebate dropping the card $25 less than the Sapphire meaningful to you? Or, is the higher factory overclock speed and more widely known Sapphire name for AMD GPUs more meaningful? Now if both GPUs were priced exactly the same, I'd have to seriously reconsider