I'd go P4 for several reasons:
1. More stable. (below is a quote from Tom's hardware):
"Another factor is the stability and product quality of a system:
while all Athlon processors suffered from occasional instability in
our tests, the Pentium 4 platform ran without a glitch."
Statements like that are hard to quantify. I have an ABIT KT7-RAID going on 58 days of uptime. Is that unstable? The only time I have to reboot it is for a Microsoft update. Without knowing what the instabilities were and on what motherboards this is meaningless. In the many reviews of the Tyan K7 Thunder it has been shown that their stability is unquestionable.
2. Upgrade path.
AMD appears stuck at approx. 1.5 Ghz, yet Intel has retooled for .13 Micron which will give a socket 478 MB a path to 3Ghz or higher.
The 1900+ runs at 1600Mhz stock. The Thoroughbred will use socket A as well, and there has been no evidence thus far that they will be incompabtible with existing boards.
3. Memory choice:
Have it your way with P4. DDR, SDRAM, or Rambus.
Until AMD acts upon their license for Rambus, this is how it is. Few will argue the benefits of RDRAM over DDR however. In real world applications its virtually nill. Intel's support of DDR in the next year will be at least equal if not greater than RDRAM.
4. Overclock:
If you choose to OC, it's no brainer with P4. Buy a couple notches down from the top and than crank up FSB. P4 1.7's are rock solid at 1.9 and higher. Intel spec's it's CPU's more conservative than AMD which gives you more OC gain if you choose to do it.
With AMD chips not only can you overclock the FSB but the multiplier as well. This is simply not possible with Intel CPU's. Even if Intel is more conservative when they bin their CPU's, that doesn't mean you can't overclock AMD chips as well. Some AMD chips reach 50% of their rated speed with appropriate cooling. Your chances of getting that with an 1800 or 1900+ are less likely though, at least until the Thorougbreds come out. But again, megahertz is not an accurate measurement of performance. This is especially true with the P4.
5. Better thermal management:
P4 throttles down in an overheat situation. Athlon self destructs.
No argument there. Intel's thermal management is excellent. Your Athlon won't self destruct however. Unlike Tom's test, simply setting the BIOS to shut down at 50-60C will prevent your CPU from being fried. It's not as accurate as the on-die thermal diode, but it works.
6. Noise:
The Intel supplied heatsink/fan is very quiet.
On the other hand Athlon has slightly better price/performance but the differences aren't that significant. Another quote from Tom's Hardware:
"In the SiSoft Sandra Benchmark 2001, the overall performance is
uneven - both Athlon XP and Pentium 4 switch places several times".
Generally speaking, I like the HSF Intel provides over those of AMD. As pointed out earlier though, a 2.0Ghz P4 will run you $432, a 1.6Ghz Palomino with a good HSF will put you out $275 or so. In the end, you're going to have to decide what meets your needs best. Take comfort in the fact that these days you have a choice...that wasn't always so. I'll leave you with this, from Tom's hardware:
With its new Athlon XP 1900+, AMD has widened its lead in performance even more. In virtually all the benchmark disciplines we re-selected, the Athlon XP 1900+ takes the gold. The Athlon XP 1900+ is especially effective in CPU-intensive situations, for example audio/video encoding or classic 3D rendering. However, we have observed an important trend in this area: the frequent appearance of application patches and updates that increase performance of the Pentium 4 via SSE2.
Intel's efforts to gain a foothold for SSE2 in the market are beginning to show results, although it still cannot be claimed that SSE2 has really established itself at wider level. For the typical office user or gamer, the extra performance offered by Intel's fastest processor (Pentium 4/2000) makes only a marginal difference when it comes to practical applications.
However, the difference between Athlon XP 1900+ and the fastest Intel processor - the Pentium 4/2000 - is, realistically speaking, minimal in most cases. There is still a clear argument in favor of purchasing the Athlon XP 1900+ speed-demon - its price: AMD is launching this processor at a price of 265 dollars. The fastest Intel processor costs 400 dollars with fan (boxed version).