Vapor-X, the XFX black edition is just a customized reference design rather than a fully custom solution like the Sapphire.
Also its a Ghz edition card, which the XFX isnt. Better performance from the newer BIOS.
Provided your running Eyefinity with uber resolution monitors.
Plus, at that massive resolution. A single 7970 would be choking on its own blood trying to keep up, you would need a 2nd (or 3rd) card to perform decently at that level. Which then gives you four (or six) possible outputs that support that resolution.