For more multitasking room and video encodeing yes the quad would be a better choice. The OP asked what would be better for WOW and MW2 the phenom will give better performance out of the 2 chips he listed. I would suggest that Moosh should find a Phenom II x4 if he can but if he has to choose between those 2 that he listed then go with the Phenom.
yeah but several games have a 15+ fps lead with the Phenom II. The Phenom II will be perfectly fine with the games you mentioned, but cjl is probably suggesting the Athlon II x4 since it does manage to keep up in some games, and that games are becoming more and more multi threaded, which may lead to much better perf. on the x4 in the future. However l3 cache does help with gaming.
I agree go with the Athlon IIx4 if you intend to play any other games ever. But if you are buying just for those two, the Phenom IIx2 is your best choice.
Edit: Isn't WOW one of those games that keeps changing? Does this not mean at some point perhaps it will be more core optimized?
Yeah thats why I was thinking the Athlon II x4 might be better in the long run. Also the call of duty games for PC (at least world at war to my knowledge) have a multi core rendering option in the graphics menu.