Which CPU is better?

Which CPU is better: The Intel Core 2 Quad Q6600, or the Intel Core 2 Quad Q6700? Both have an FSB of 1066MHz. The Q6600 is cheaper than the Q6700 by $40, and is slower by 200MHz. Does 200MHz really make a difference? I was wondering because I want to buy a new motherboard and CPU with an Intel Core 2 Quad that I would use for gaming. Thanks for any help!