Q: Well, I have two computers, one has a 2.0 GHz Dual Core Processor (Pentium E2180) the other has a 2.8 GHz Pentium 4. The other hardware to go along with either processor will be 3 GB DDR2 ram, GeForce 8500GT video, either XP or Vista Home premium with aero disabled.
A: The 2.0 GHz dual core is better. I would suggest getting the 2.4 of it though (E6600 I think, can never remember numbers anymore). People act like the dual core won't help you, but it helps a LOT. Your operating system will be able to do it's thing on one core while your game is sucking up the other core. That way you don't get OS lag. It's also nice to be able to have a web page up on one screen while gaming on your main screen without having to worry that the ad on the site is going to lag you at the critical moment. Also, you can overclock the dual core chips up to about 3.4 GHz easily.