The 6700HQ has a base clock of 2.6GHz, and will clock up to 3.5GHz (on one core) if power and temperature allow it. I can't find what the 2, 3 and 4 core turbo clockspeeds are, but it needs to stay within 35w so a tiny laptop cooler can keep it cool. A desktop 6700 has 65w to play with, has a baseclock of 3.4GHz, and will turbo up to 4GHz. I believe it's 4.0GHz on one core, 3.9 on 2, and 3.8 on 3 or 4 cores.
I would not put a desktop CPU in a laptop chassis. You're just asking for trouble. If it needs to be a portable machine, go for the 35w chip.