There are a few differences. they perform very similar though.
the EP does not have support for PPGA Celerons as well. and no on board video, altho onboard sound is optional. I just picked up an Asus CUSL2-C on the i815EP and I love this board! so far very stable and not too many hassles either.
I'd recommend one of the new i815 solutions they seem to be quite good!