I was an Asus diehard until about a year and a half ago.
Tried an MSI, loved it, built a few more MSI's, loved them.
MSI rules, all around, for stability, overclocking stability, features, documentaiton and quality.
I had 2 bad experiences recently with Asus, the CUV4X and the CUSL2. Both had some rather serious annoyances related to voltage and temperature, so Asus just doesn't cut it anymore for me.