I am biased, I'll admit it. I say get the Microsoft Intellimouse Explorer 3.0. I have owned all three versions of it and the difference from versions 1 and 2 to version 3.0 is, although cliche, night and day. The new version of the included Intellipoint software also allows you to set each button's functions for different programs. The mouse is very comfortable and works in Quake 2, Quake III, Half-Life, etc......... in a way NEVER thought possible with optical technology. I have a hard surface to track on my desk and that is why versions 1 and 2 of the mouse failed. Version 3.0 amazes me.
Now, after I tried to sell you the one that I own I have to admit that I've only heard positives about the dual optical mouse from Logitech. It's not been reviewed as better, but it's been mentioned to perform at the same level of version 3.0. Therefore, either one should perform great. Just stay away from the cordless ones