They are both great boards. The Asus justifies it's self on price though. Whatever, if any, performance gain you might see from the Gigabyte wouldn't justify the doubling in costs. Also it seems that some of the increased costs of the Gigabyte are from the added ports (more SATA6.0, Firewire, etc). If you don't need more ports don't buy them.
I'd also check out the support forums for each, see which community is more active if you plan to do some serious tweaking with your hardware.
Both are excellent and very much durable.. But these boards are more geared towards being extreme overclock friendly.. I guess that's not your field of interest.. Anyways, Asus gets my vote over here.. As a side note, if i can divert your attention from Asus and Gigabyte for a moment, i'd like to mention the MSI BigBang XPower X58 as a potent option.. Btw, how many cards are you planning to use.?