AMD, I've used it since my first gaming rig back in 1999, my first system was intel when i was about 7, when i turned 8 I was given a choice, I chose AMD based on wanting to be different, all my friends parents had intel boxes, I wanted an AMD sticker.
Now that's definitely not the reason now, I've stuck with AMD and I've always seemed to come out on top, I've built many rigs for people and the ones who choose AMD are always happy with them, and they don't spend boo koo amounts of money.
Don't get me wrong Intel is great, and the rigs I have built with Intel have been pretty amazing, but they've cost a pretty penny.
But I love my AMD, it never sees over 52*C full load on air, and oc'd a bit, my whole rig under full load stays in the 40-50*C range.
None of my intel boxes i currently have or have built have ever done that.
Of course the newest intel i own is a 65nm presler.
But it all comes down to what you want to spend and what you want to do. I would highly recommend a new Phenom II quad core, i just built my buddies system as follows and it annihilates everything
EVGA nForce 790
8gb ocz ram
2 GTX 295's (at $600 each not really in the price range of anyone, but he wanted to go big. he wanted 3, i told him he was dumb xD)
Phenom II 965 BE
now im sure you wont go off and build this, but its a hella powereful AMD system
It powered through anything we threw at it, Crysis isn't as pretty as you would hope maxed lol