ASrock = good BIOS, good compatibility, good features.
Definitely NOT Asus, at least not for m/b. Reasons?
1. Zero support for anything but Windows - in other words, if you buy Asus you will have to marry Microsoft. Else they won't warrant any hardware or BIOS specs.
2. Buggy BIOS - at least they've fixed some now.
3. Incompetent technical support.
4. Lousy documentation, including incomplete manuals (incl. ROG), antiquated compatibility charts, useless release notes, etc.
5. Extremely bad warranty service in the US - search the web for plenty of horror stories.
6. Overpriced.
Mind you, I only refer to motherboards. I'm very happy with my Asus Xonar Essence sound card (as long as I don't need their warranty or technical service).