For me, it’s usually the chipset that determines how stable a board is. I prefer Asus because they add a ton of great features and are rock solid. I can’t account for Asus’ nVidia-based boards, however.
Nearly every nVidia-based motherboard I have has failed in one way or another. Either the network port goes (which is tied to the nVidia chipset), or other components fail, or the motherboard just fries.