Well, like I said before: First-hand knowledge is a lot better than giving advice based on what other people say.
The DFI board you picked out will destroy the Gigabyte in higher-level overclocking. No questions. Also keep in mind that there is a huge amount of RAM timing, etc options on the DFI that can befuddle even experienced dudes. But, because of those timings, and because of the high available Vdimm, you are able to do some nice OCs with the DFI board. It has been said that the DFI boards have very good quality, but again, I cant tell you this from 1st hand knowledge/experience.
Now, the Gigabyte, like I said, is very stable, etc etc. I have done some slight OCs, but using generic RAM, so it didnt turn out good. But, if you get the proper RAM, that can stabily OC with low voltages, than the Gigabyte should give some decent OCs. I can vouche for the quality on the Gigabyte board as being good, from what I can tell. The Gigabyte also is usually a couple dollars cheaper than the DFI.