Wireless one is heavier since it takes 2xAA batteries.
In terms of functionality, they are exactly the same AFAIK. The laser on my wireless one sometimes annoys me, since you can lift the mouse up to about 10-20mm's off the table and it still works - so if you moved the mouse across your desk and ran out of space to move it so you lift and it and put the mouse back in the centre of your desk/table, the bloomin cursor follows you unless you lift the mouse high enough.
Guess it's not much of a problem since the mouse is sensitive to motion speed - faster you drag the mouse across the screen, the quicker the cursor goes in a shorter amount of desk/table usage than if you were to drag it slowly across the screen.
Do tell me if I make any sense at all