14 DAY TRIAL // The X4000 and X5000 aren't all that different from each other and, indeed, they look mostly the same, but they are distinct peripherals nonetheless.
The X4000 has a regular scroll wheel and a battery life of up to 30 months, while the other one has a touch scroll and up to 24-month life.
Power is provided by a pair of AA batteries and the prices are of $29.99 (23.07 Euro) and $39.99 (30.77 Euro), respectively.
The wireless connection to the PC is accomplished over the 2.4 GHz band, while the operating range is of up to 30 feet (about 10 meters, give or take).
Finally, both mice have 1,600 dpi laser sensors and come with micro receivers that can connect up to five devices at once (save USB ports for other things).