their all pretty much the same as far as performance. usually the different companies use custom pcbs, heatsink/fan, and clock speeds. for example the msi power edition gtx 660 ti you can overvolt the gpu to give it more power to overclock more. for a gtx 660 i would get the msi twin frozr overclocked as it runs cooler then most of the others. all the gtx 660s are usually within a couple fps between eachother.