I was wanting to know which to get for my upcoming build. I will be doing mainly gaming with light video editing on the side. I know that the XFX comes with never settle bundle of 4 games and the R9 doesn't. But the R9 is "new"/ rebranded and has mantle. The R9 is cheaper. I don't plan on over clocking very much is even that. They are very close in the benchmarks.
The 7950 is much more powerful that the r9 270x and you get the never settle bundle.
The r9 270x is basically a 7870, whereas the 7950 is more equivalent to a r9 280x
Bottom line is the 7950 and 7870 are going to drop in price soon due to the fact retailers will want to get get rid of them, so forget the r9 270x
Also because Mantle runs on the GCN architecture, it will be compatible with the HD7000 series (will try an find a source for this).