Intel or AMD...what an interesting question. And my highly simplified, distorted and biased answer:
It all depends on what you're doing with the computer, of course, and also on the time at which the purchase is made (i.e., 3 years ago, Intel ruled, last two years, AMD is supreme, in a couple of months, Intel takes the title back) and if you're asking about specific chips or an 'overall' type of question.
As of now, before that sweet Intel chip comes out, overall AMD is the winner. For servers, they've got Opterons that are superb. Desktops, you've got the Athlon series. Athlons use less power, produce far less heat, and produce more work than most Intels. On a computer system that is not used for heavy graphics rendering or serious multitasking (serious as in compiling a database while rendering a 3D movie and ripping a DVD at the same time, not to be confused with having IE and Outlook open at the same time) or a computer that is used for gaming, the AMD wins. Multitasking, the Intel wins, due to hyperthreading.
Basically, it's hard to beat an FX-62, or an X2 4800. It's just really really hard to do. HOWEVER! Intel does have chips that can do it, it's just that they tend to warm up the room...and the rest of the planet. Or am I the only one seeing the connection between number of Pentium processors in use and global warming? Eh. It's a good theory, really.
Then again, we have the occasional oddball which throws a curve like no other. The Intel Pentium D 805 chip, to be precise, a dual core P4 at 2.66Ghz. That cute little chip goes for about $120USD at NewEgg right now. With a STOCK P4 cooler-STOCK mind you-and a motherboard that will let you tweak the settings, you can over clock it to 3.6Ghz. Stable. With something like a Zalman fan, you can get to 3.8 or even 3.9Ghz. Above 4Ghz, though, you pretty much have to have water cooling, and 4.1Ghz has been reached. And stable. Tom's Hardware, you really rock. And you're insane, but still, a dual core 4.1Ghz Intel chip for $120...wow.
Before the 805 was 'discovered', Opterons from AMD held the overclocking title belt. Probably due to them running cooler compared to the Intels, they can be overclocked to downright silly speeds (somewhere on the net is a video of a fellow using liquid nitrogen, I think it was, as a coolant, and reached around 6Ghz. I think. Been a while) Realistically, an Opteron at anything over 3Ghz is blazing fast. Really really fast. And you can actually afford to buy a board that sports FOUR of those cute little Opterons. (more than four, it gets kinda outrageously expensive rather than just really expensive)
Now, Intel's next chip that comes out is going to be really interesting. There's not a lot to go on so far, but everything points to a chip that is low power, low heat, and 20% faster than anything AMD has. I plan on using one in a box I'm going to build specifically for Vista. I also plan on snagging a nice AMD chip, one of the new socket AM2's with DDR2 support, put it in a box with Vista, and maybe run some benchmarks. (who am I kidding, I have no time for benchmarks. Whichever system feels faster gets to keep Vista, the loser gets XP)
Yep, I'm wishy-washy when it comes to CPUs. I'll take whatever is stable and does the job I ask it to do. Right now most of the computers in my house (there are, um, nine in operation) use AMDs, though two of my three servers use Intel. Next week, it could be a different story, as long as it works.