Keep in mind that an increase in antenna structure/height will have a MUCH GREATER effect on your signal as received by others than an increase in power output will. For example, if using a 5-watt handheld and a 50-watt mobile into the same antenna, the best that the person receiving your signal can expect to see is a 10 db increase in received signal for the higher-powered transmitter. On the other hand, if you take a 5-watt handheld rig transmitting out of it OEM "rubber ducky" attached antenna, and then take that same handheld rig and connect it to a good, properly-mounted, mobile antenna, the received signal strength that someone receiving your signal will dramatically increase.

IOW, when comparing how a handheld 2m transmitter "gets out" to how a properly-installed mobile 2m transmitter gets out, the lion's share of the latter's better range comes from its better antenna system, not from its 10-db increase in output power.

I've know a lot of ham operators who want some basic 2-meter service available in several cars. An inexpensive solution is to install a good antenna system in each vehicle, and then use an electrical co-axial cable adapter to allow a handheld transceiver to be connected to the PL-259 antenna connector on each vehicle.

Naturally, if money is no object, then installing a dedicated mobile 2-meter, or dual-band or tri-band, transceiver in each vehicle is a lot more convenient. But one of the low-cost advantages of the "adapted" method is that, when on the trails, one can disconnect the handheld from the vehicle's antenna system, connect the OEM rubber ducky antenna to the handheld, and then exit the vehicle and stay in communication with other stations while walking around. Having a handheld is particularly advantageous when talking someone through a rough part of the terrain, particularly when the distance between the observer and the driver is such that even shouting is difficult to hear.