IMHO the Gigabyte cooler is overrated. Its loud, and rather inefficient considering it has three fans. Even Sapphire's Dual X (Two fans) beat the Gigabyte cooler with three fans on the 7970. People seem to think more fans is more cooling performance, this is clearly proven wrong in Gigabytes 7970/680 Superclock models. The card is massive, loud, heavy, and has a terrible cooler.
The asus cooler is fantastic, like I've seen one in action, and there was basically no noise change from one idling to one in load. It gives you alot of headroom to increase voltages, as the cooler is much better.