first one
second one
They are basically the same processor, but I believe the E models are newer and addressed some of the heat issues with earlier Prescott line processors. Personally, I wouldn't buy a Prescott at all though.
Is Prescott before or after Nothwood?
I'm running a P4 Northwood, 2.8GHz, No HT. So the 200MHz isn't significant, I know, but I multitask a lot (hell.. iTunes) so that'd pick up some nice slack. And I plan on giving my processor to my brother, who's got a 1.8GHz and needs an upgrade badly.
It sucks because we're confined to the 478 socket.
EDIT -
Assuming I'm blind, which processor would you buy? I don't know what the specifics are on my board, but I can give you a CPU-Z export on request, and I can tell you right now it's a Dell Dimension 2400, although I know that's not specific.