Good question, they are all pretty good boards! I've also considered these boards for my next upgrade, I decided to go for the MSI Delta-ILSR. Asus is pretty reliable but bad tech support. Abit has good overclocking. But I've heard MSI is best for performance, which is why I decided to go for that board. Hope that helped a bit.
<A HREF="http://www.anandtech.com/mysystemrig.html?id=24106" target="_new"> My System Rig</A>
<A HREF="http://service.futuremark.com/compare?2k3=535386" target="_new"> 3DMark03</A>