Single card performance there won't be much difference. I have a Sapphire 7950 and its extremely overclockable especially with a custom fan curve(1150MHz Core and 1450MHz Memory in my case). Comparing my results to a friends overclocked Gigabyte 670 there's usually about 5ish FPS difference. I can also attest the Sapphire is very quiet with fans 0-70% and 85-100%. Mines whines a lot around 75%, but above or below takes care of the issue. And obviously, at 100% fans any cooler is going to be "Loud".
With those games you'll have no problems maxing any of them out. I play BF3 at 1920x1080 fulled maxed with 65+ frames easy. Metro 2033 Maxed causes a few drops here and there, but still very playable
As a side note: When comparing bench reviews on both of these cards, be careful. Certain software/hardware setups favor one brand over the other. I found in my case, my 7950 performs far better than the benches said they would. Also, the Sapphire is NOT voltage locked, allowing more overclock room if you've got significant cooling.