What is the difference between CAR and trekking GPS? the main difference is the power source and the software that is loaded. Car gps systems will be set up to use 12VDC, and typically be hard-mounted into the car. Trekking gps (portable) models will be battery operated, so voltage would be anywhere from 3-9VDC. Since a person will have to carry it, the portable GPS will typically be smaller and lighter.
Regarding software, Car units will be more likely to have better information on roads, addresses, attractions etc while the hiking …