DFI is known to be a really good OCing board. Can't really go wrong there. They have alot of voltage options and other thingsl ike Memtest built into the BIOS...plus they release alot of BIOS's, beta or otherwise.
I'd say DFI for OC'ing but hey I'm sure you'd hit 2.8 on an ASUS board, they do pretty well. Its just the DFI ones won't have your RAM limiting you 'coz you can hit 4.0V on the memory voltage
