The i3-2100 definetely. Plus, with the LGA1155 platform, you'll have upgrade options (Ivy Bridge) in the future, whereas the AM3/AM3+ platform is dead for most of us, AMD stopped shipping Phenom II/Athlon II, and i don't have to tell how much Bulldozer has failed. So the i3-2100 and LGA1155 is the way to go.