The wireless is 1600dpi laser while the wired one is 800dpi optical.
IMO:
If you get an Apple computer so you'll receive one of these mice no matter what, you might be tempted to pay more for the wireless. Weirdly, it does have a sensor far superior to the wired one's sensor. But seeing how the difference is more than the price of a basic $15 Logitech mouse, which has superior usability to both Mighty Mouse models, you should pick the wired MM. Consider it a sunk cost and throw it in a drawer as a backup. Alternatively, you could sell it.
Comments
IMO:
If you get an Apple computer so you'll receive one of these mice no matter what, you might be tempted to pay more for the wireless. Weirdly, it does have a sensor far superior to the wired one's sensor. But seeing how the difference is more than the price of a basic $15 Logitech mouse, which has superior usability to both Mighty Mouse models, you should pick the wired MM. Consider it a sunk cost and throw it in a drawer as a backup. Alternatively, you could sell it.