Originally posted by: Kernel32
Logitech MX 1000 Laser. Worth every penny.
Yeah...that was one of the OP's 2 options...
To the OP: I'd go with the Intellimouse Explorer. Much better value, there's a tilt wheel, plus you can't really see it in the pic, but there's two left side buttons.
Edit: And before you go thinking I'm some MS fangirl, I don't own the Intellimouse Explorer, I use Logitechs exclusively. But I've tried the IE out at a store and liked it, and if wasn't for the fact that my MX500's smaller size fits my hand better, I would have gotten the MS one.