An XP overclocked to about 1.8-2.0 could whomp a P4 2.5A. The Palomino can in fact continue beyond 1.73 ghz but AMD has other plans for the XP. The Thoroughbred core will prove to be quite the contender, especially having a .13 micron process, now it will be able to overclock like hell.
RDRAM is faster than DDR by quite a long shot. It's usually 100mhz ram, in QDR operation, but there's a 133mhz variant around the corner. At least, I think there is. I don't catch up that easily on the Intel side of things.