well, first of all, if u want the K7N2G, ur gonna have 2 wait a few more days (or so im told). that's the board i want, but im not waitin a day after the 10th. if it ain't available sometime within that limit, im buyin the Nforce2 based leadtek board.
i think the NForce2 chipset's better. and i think the K7N2G is better'n the KT4 ultra. go 2 the msi site and compare them (if u didn't do that yet).
and of course, it depends on what u wanna do with ur computer. i dunno how up2date this guide is, but check it out. it might give u some kinda idea:
http://www.msi.com.tw/html/products/buyers_guide/buyers_guide.htm