For now, the E8400 is better. But in the future, when applications and games start to take advantage of more than two cores, the Q6600 is better. So you should get the Q6600, if you're not looking to upgrade for a while. If you upgrade like every year, the E8400 is the way to go.
An E8400 at 4GHz would probably be faster in games than a Q6600 at 3.7, but 300MHz isn't really that big of a difference. Plus, the Q6600 has an extra two cores, to handle other things.
An E8400 at 4GHz would probably be faster in games than a Q6600 at 3.7, but 300MHz isn't really that big of a difference. Plus, the Q6600 has an extra two cores, to handle other things.