I would grab the Gigabyte board, the pcie slots are farther apart meaning lower temps in sli/crossfire as one card isn't starving the other. Not to mention the placement of that Cmos switch on the asrock board is extremely retarded.
Asus might OC better though because it has 4+8 phase power while the others only have 6 phase (asrock has 4+1+1)
I would still go with the gigabyte though.
edit: Scratch that asus might be better thing, I can't see any heatsinks on the VRM (this is might be due to there website not letting me view any other images then the cover image...)