Before this turns into an AMD vs Intel flamewar, let me just point some things out :
1) compare only cpu's that cost about the same. This is the only real criterium but yes, Intel fails there too
2) The P4 Prescott is the hottest chip ever, there's quite a few systems where it runs so hot, it automatically throttles down to a lower speed to lower the temp. This technology was meant as an extra feature to protect people from burning up their cpus, but now people are running slower than they should and they don't even know it
In older processors running this hot would cause a crash, but the p4's stay running (although a lot slower)
3) The Athlon64 on the other hand is the coolest chip I've seen in quite some time. With the DEFAULT heatsink it runs at about 45 degrees celsius, while the Prescott would hover near 70 (which incidentally is the temp where it starts to throttle down the speed). I've made a silent pc for a customer of mine, where the cpu fan regularly just STOPS completely (by design) when the cpu temp dips under 40 degrees celsius. Trust me, the Athlon64 chips are really good, and they all seem to be able to overclock atleast 400 Megahertz (depends on your motherboard).
4) Did I mention that the Athlon64 3000+ makes mincemeat of the Prescott 3Gigahertz ?