People will reccomend what they own. . .
Either of those boards will do a great job, the Abit AB9 QuadGT is better in terms of raw performance but again you wont even notice it, its all down to benchmarks.
You wont see any difference if your gaming & everyday use etc, if its down to money pick the Gigabyte & thats from someone whos only owned the Abit AB9 QuadGT, if you dont mind paying extra money buy the Abit.