Hi chaps,
Well here goes, here is a bit of info about radio. I don't think it will help to make the choice but it should explain some of the limitations.
Power output: 5 times more power does NOT give 5 times more range. Twice if your lucky, range is dependant on a square law.
PMR446 radios: A lot of these have 0.5 Watt output (the maximum allowed) but some cheaper ones have only 0.1 Watt output. More important is the performance of the antenna, the helical antenna fitted (rubber duck) is not an efficient type of antenna, particularly when used close to the body.
Body absorption of the radio energy is greater with PMR446 UHF than 2m VHF. For any body worn radio try to mount it so the antenna is not right up close to the body.
When on the ground the PMR446 signal will also be absorbed/ blocked more by trees and buildings, apart from the lower output power, when compared to VHF.
PMR446 is effective for short 'line of sight' paths but don't expect much more.
Having just looked up the price of cheap VHF and UHF hand helds on e-bay I am not surprised by their popularity, pity they are illegal to use without a license .
Safe flying,
Alan