I have very little experience with computers beyond using them and looking up components. For my first build, I plan to use either an Intel i3 550 (although I am considering an i5) or an AMD Athlon II X3 460. I understand that the AMD processor is cheaper, but I'm not sure that relates to its performance compared to the i3's. The computer I plan to build will mainly be used for gaming, and will hopefully run Battlefield 3 on High settings at a good 720p resolution. Will these options even handle that when paired with an ATI Radeon HD 6770?
BF3 becomes a very CPU bound game when going into online play. Many other games like Skyrim, World of Warcraft and Assassins Creed Revelations are very CPU heavy games. So going with the i5 is your best bet imo. I'm buying the 2500k one and overclocking it. Those games will use your GPU but only a certain percent of it.