radio

Firstly, for your boat you need to know your area of use and if you are near a VHF repeater then you have a far better range than UHF.
UHF is only line of sight, in other words you basically need to be able to see the receiving station. Also UHF is prone to atmospheric conditions affecting it's range.
I have used a VHF handheld marine radio and was able to trigger the repeater some 30 -40 km away.
For your vehicle, unless you have access to a private frequency UHF is the go, however you can't use the Marine frequencies on land based activities.
So you may have to buy two(2) radio's, once again the prices are varied depending on the make and model.
hope this is of some help