Go for the 9000 for sure. It's actually slower than the 6700, but uses less than half the power. The 6700 is a desktop CPU at 2.66GHz, and rated at 105W. The 9000 is a laptop CPU at 2GHz, but it is only rated at 45W. It is by far the better choice, and will run much cooler with a much longer battery life, while still giving the power of a core 2 quad (albeit one at a slower clock speed).
The trend of desktop replacement being marketed as a laptop is really worrisome. e.g. the Q6700 being discussed here
Just because they put a battery in there doesn't mean it's a laptop, more like a UPS.
Another consideration here is what software you intend to run on the laptop. Is it capable of using 4 cores efficiently? Looking at Intel's current price list (6/2/2009), the Q9000 (4 cores, 2.0 GHz) cost $348. Also listed for $348 is the P9700 (2 cores, 2,8 GHz). Personally, I would lean towards the P9700.