Athlon 64 bit processors will run apps and games great now and even better in the near future with 64 bit Windows XP comes out. When games go 64 bit it's going to be fantastic!
To answer your question, a 3.0 Ghz P4 with HT @ 800 FSB is faster. The
PR ratings given to Athlon XP processors mainly apply to the older 533 FSB P4's and less.