If you intend to game on it, then get an AMD.
Intel CPUs generally have an edge in content creation (image and movie editing), and a kind of simulated dual-CPU setup called HyperThreading. It can in some cases make the system as a whole a bit more responsive (note: it's just from what I've read. Never owned an HT enabled Intel myself). Of course, if you have the cash, you could just get a dualcore AMD, and Intel suddenly have much much less of an advantage.
For most other stuff, it won't really matter that much. You can potentially get a cooler and quieter system if you use a recent AMD versus a recent Pentium (excluding the Pentium M), since the AMD chips are much cooler (less need for noisy fans), and draw less power.
Bought a Athlon64 X2 4400+/2x2.2GHz recently (which replaced a Athlon64 3200+/2.0GHz). Couldn't be happier with it.
Disclamer: The last Intel I owned was a Pentium MMX, and I've used AMD's since then, so I could possibly be a bit biased (though I try not to be).
Edit:
CanadaRAM: Seawhat?
Never heard of it.
I've had no issues with my Athlon64 (nor my Athlon64 X2) and it's on 24/7.