Increasing output wattage on a uhf

[the evil twin]

What is the benefit of having a higher wattage unit for in car 4x4 coms,
in a UHF radio???

As others have said, bugger all in 99% of useage.

Whilst illegal the two situations from personal experience that may benefit are...
On some of the large Cattle/Sheep stations where the base antennas are up a hill or a tower and can hit you but not the reverse.
When operating as a relay for outback travel or long track 4WD racing checkpoints etc.

It is better to go 5/25 watt licenced VHF but using tweaked commercial UHF or dual band UHF/VHF sets is way cheaper.