I have both a Logitech G7 and a MX Revolution. Both of which I like better than my old Razer copperhead, mostly due to the fact that they are cordless. As far a DPI I never really noticed a difference in accuracy between laser mice, other than the movement sensitivity which can be controlled on any mouse and never had a reason to control it on the fly.
The thing I think makes the biggest difference is the mouse pad surface and the mouse feet. You should have a hard smooth surface, I personally use a "
Icemat" but some may not like it due to the ceramic sound it make when you move the mouse. Also use Teflon mouse feet, which most gaming mice come standard with (MX revolution doesn't though it’s also not a “gaming mouse”).