When I think of P4, I primarily think of it's days in competition with the K7 AthlonXP, not the Athlon64. K8 was a very different chip and seems to represent the dawn of a different era to me, though I realize it did overlap with the late P4s. So if we're talking Prescott vs K8, yeah the K8 is definitely a better CPU. I love the K8.
Athlon XP wasn't convincingly superior to the P4, but it's great appeal was that it was cheap. I never would have spent the money on a P4 back then, but that's not an issue anymore. Therefore I find I'm more able to take interest in P4s today.
P4 has better chipsets and I believe it generally is easier to find high quality boards for it. Athlon boards were mostly designed for low income gamers who wanted performance for the least amount of money. I include myself in that group, and it did the job but I don't think it proved superior to P4 outside of the cost issue. When factoring in the motherboards and chipsets, I think P4 was more ideal for somebody who didn't mind the cost.
That said, Athlon boards did get better over time. They started out pretty awful ghetto IMO, but by the time you get to the nForce2 they had some really nice ones.
2 or 3 years ago I was looking into building a file server and considered a bunch of options ranging from P3, P4, Athlon MP and K8 boards.
There are good P3 server boards, but I wasn't satisfied with their PCI bus limitations. I didn't find many options for Athlon MP and it didn't seem to have good server chipsets available, the AMD 760MP was really for workstations. They had similar PCI limitations as the older P3 boards I had looked at.
I was impressed by the P4 Xeon boards - good ones are easy to find and cheap. They had way more PCI-X capability than AthlonMP boards, so it's easy to see why nobody built AthlonMP servers back then. AMD didn't become competitive as a server platform until the K8, which was quite a revolution.
Even for workstations the AthlonXP is still a bit challenged because high end software was carefully optimized for P4. Athlons were mainly competitive in consumer apps because those apps probably weren't as optimized in general. Inexpensive consumer software would not see the level of careful optimization that was required to get the best out of a netburst chip. The Athlon wasn't as sensitive to optimization, and that fact is it's strength.