Q9550 Pros: 45nm stepping runs cooler Uses less power Good price
Q9550 Cons: Not as fast stock speed No unlocked multi will not OC as high
Q6700 Pros: Good Price average stock speed
Q6700 Cons: 65nm process will not OC as high as the QX6800
Overall with no price the QX6800 is great. But for the price its not. The Q6700 is good and will OC decently but the Q9550 has a newer process and is about 10% faster clock per clock as well as it will run cooler than the Q6700 at the same clock.
Its not an easy choice. What the hell..... get the Q6000.