I hope you are not considering either processor for a purchase.
Here is a good
review. You decide for yourself which one is better depending on the application.
Either way consider they cost as much as almost 3 A64 3200+, or A64 3000 + Radeon 9800Pro + 512mb OCZ 3200 2-2-3-5 RAM + 1 WD360 Raptor + SLK-947 or Zalman CNPS7000 heatsink; you have to be ON CRACK TO BUY EITHER.
And if you do have money to burn, A64 3400+ together with an awesome watercooling setup will still be better. Heck, P4 3.2ghz @ 4.0 on watercooling will be better anything but those 2.