That's a really hard choice tbh. When I was faced with this choice I went for the Gigabyte Windforce 7950 3GB for a BTC rig. If having to make that choice again I'd likely go with the same card. This is mostly on account of the superior cooler (which is an Arctic Cooling Accelero in all but name only).
I'm not a fan of the Asus card because of the 3 slots it takes and I don't see that as being a better solution seeing as all Radeon HD 7950s tend to cap anywhere between 1,150 - 1,375MHz with the cooler rarely ever making a difference.
The MSI boards tend to have top quality components and I do enjoy my Radeon HD 7850 2GB Power Edition tbh.