They're both slot-1 motherboards. I don't know anything about the p3v133 but I've had a slot-1 550E running fine in my kid's p3v4x at 803 MHz. for months. The p3v4x has a newer VIA chipset, at least according to ASUS' web site. This is a bit of a controversial board. I don't know how well a slocket works in one, but <A HREF="http://www.overclockers.com.au" target="_new">http://www.overclockers.com.au</A> have a formum devoted to this board.
Asus also have a cuv4x, a socket 370 board that's supposed to be pretty good, though I've not used it. My personal practice is to avoid slockets becasue I don't want to add something else that could go wrong. I might have to change that, though, when I upgrade as the 370 Pentiums are becoming more abundant...esp. the new stepping CPUs.
Mike