I have only owned Asus/Asrock and Abit boards until I got my DS3.
My overclocking experience has been good with the Gigabyte board. I have a 6400 running at 3ghz with 1.3v.
As far as cooling, I do have a fan aimed at the nb. I had read so much about it getting hot I went ahead and set up a fan.
I would buy the board that has the features you want. I don't think you can go wrong with either. However, some claim you can get a bit more of an overclock out of the Asus.