r9 280x gigabyte or asus

ASUS is an extremely reputable brand, at least in the states. I however have personal experience with Gigabyte as I've got a gtx 780 from them, and it is extremely good, I have not been able to get ti to pass up 65c at an 1175 OC and even then it is still extremely quiet even past 50% fanspeed.
 
Coolers aren't really much different, but the gigabyte one is cheaper and comes with BF4 so i would get that. In the real world you won't realize any real difference between the two :)