For a game like BF3 the Athlon would be a much better choice as it is threaded for more cores.
But doesn't the I3 550 have 2 "imaginary" hyperthreaded cores? When i did sys requirements lab on the downstairs PC it met the recommended BF3 settings of QuadCore, despite being a dual core. So technically, the I3 550 has same number of cores, except its individual cores are alot stronger and it has an L3 cache of 6 MB, so wouldn't it be much better? Also, from Anandtech benchmarks, the I3 always scores higher in FPS than the Athlon ii x4. Correct me if im wrong but are you sure the Athlon will do better at BF 3 with its weak cores in comparison to the I3 550?
Also, can someone tell me how much does having a high end CPU matter? Like say if i upgraded to an I7 right now (which i wont) will i get a HUGE increase in FPS?