Just wanted to let you know you linked us to your shopping cart which is not accesible to us as it shows up empty. Anyways I would go with the i3 if your choice was limited to those two. However if you want excellent performance and less of a price then go with the Phenom II X4 955 (Black edition) which can be bought for around 60-80 dollars and beats the FX-4100. Also you should avoid the entire FX series of cpus, they are not really impressive and AMD's old lineup of Phenom II's beat the FX in a variety of benchmarks. The i3 2120 will have the edge when it comes to gaming but not by far. In addition, the phenom x4 955 can be overclocked to 4 ghz given you have a decent cooler.