AMD 64's are ultimately the more powerful CPU. They are better at running games, while P4's are better at multitasking and 3d rendering and video editing and all that stuff. So you can't really say which is better when they both are better at different things. Basically, if you are gonna be gaming a lot on your comp, you get an amd 64, if you are someone who makes a lot of videos/movies/art/high graphical stuff or whatever, then you should get a P4.