I'm partial to AMD. But that's just me.

In my experience, AMD is generally a little bit more stable and cooler than Pentiums.

It has been shown that AMD is better for gaming and it's architecture lets it handle some things better, but Pentiums still top the charts in music/video apps and pure speed.

I would say go for an AMD Athlon 64 between the 3000 - 3700 range. Depending on your budget. 3500+ is a safe bet if it's not too expensive.