What made you narrow it down to just those choices? If you only buy ASUS motherboards, that is fine, but if not, I think that there are better value boards out there. ASUS generally provides quality boards, but they also generally have higher prices than many others... and no, I don't recommend ECS.
I would recommend an nForce2 chipset without integrated graphics and the better southbridge controller. VIA KT400 is slower, doesn't have as good of built in sound, and I have just had better experience with non VIA chipsets.
Like what was said before, What do you think what the +'s and -'s are?
Both will work and your computer will run just fine. Just pick either one and you will be happy.