I would go for the Abit since its got 3 step alimentation (Asus only got 2) and that will give you more stability at higher voltages. Asus used to have nice boards but the best ones are for Pentium for AMD i would go for Abit and Epox.
Abit gives you core voltage up to 1.85 without the vmodding and 200 mhz for front bus speed.
But you might want to wait for anyway. The -a versions of abit cards are sort of the SE ones, and those are more stabile and have a better performance all over. So wait for it if you're planing on buying a 333 mobo. But didn't Abit skip the 333 and went straight to the 333a this time?