Hazle :
heck of a lot more to a CPU performance in gaming than the number of cores and clock speed. there's architecture and IPC to consider as well among many others i can't fully grasp myself. note as well that most games don't fully utilize more than 2 cores and the FX series is simply lacking in single core performance compared to an i3 which matters in games. in well threaded games (i.e; Dirt 3) though, you get a whole different story.
The only thing that matters in computer chip performance is how much you paid , and how it performs for your dollar spent.
The FX will produce frame rates that are near enough identical to the intel , but it will smash it in encoding tasks
The only games the intel can convincingly win use older DX 9 game engines and there wont be any more of those .
As for power usage ...... The FX will use about 50 - 60 more watts . Its a lot till you consider a kilowatt hour costs 16 cents
The difference in running costs at full load is about 1 cent per hour
The difference at idle at desktop , or surfing the web is about a cent every week