DarkSable :
Ouch - neither of them are very good. (There will be people who say the gigabyte is great, but it's reliability is iffy and gigabyte has poor customer support.)
If you keep saving a few more dollars, you'll be able to afford a much better 670.
Palit, (Who are gainwaird) have great customer support from what I've heard. Gigabyte are great too, I've never heard anything about Gigabyte's warranty service. Customer support maybe, but they are not as bad as Asus (How such a huge company can have the worst company service in the world makes no sense to me)