Hurls, Gos and worm have explained everything very well. Stick with UHF 477Mhz as with the 27Mhz AM are out of date.
VHF and HF require licenses and some training to use the radios. HF are mainly used by 4WD in very very remote outback areas and tend to be expensive.
With UHF 477 Mhz car units the 3 - 4.5dB antennas (shorter) tend to work better in hilly areas. 6 to 9dB antennas (longer) are more for flat terrain and signals will travel longer distances. All UHF are legally limited to 5 watts maximum transmit power.
Australia has a large selection of UHF repeater stations - some govt operated some are privately operated/owned. Repeaters are generally located to throw the signal over large hills / mountains and sometimes over long distances. Emergency services will send warnings over UHF about fires floods etc.
For the hand helds go with a 1 watt or better infact the 2 - 5watt are better at penetrating vegetation small hills. The hand helds are compromised with their antenna size and you will not get the distance with them. Some of the better more expensive handhelds allow antenna interchanges ie. clip on a higher gain antenna (2db or more) to increase signal strength.
Handheld range varies upon transmit power and terrain. The .5 watt versions are good for several hundred metres. the 1 - 2 watt for 1 - 2 kms average and the 5 watt for about 2 - 5kms average, depending upon antenna type and terrain. Most manufacturers claim longer distances but that is all theoretical in ideal conditions not real world. Remember that when using a handheld within a car, some signal is blocked by the metal body of the car. Also your body / head will absorb some of the signal thus the RF signal behind you is weaker .
As for stalking with headsets I find them to be more of a nuisance. You will have to set the Voice operated Transmission (VOX) so that wind, breathing sounds and vegetation crackling don't transmit false signals theus equating to discharging your battery quickly. Secondly in thick scrub the head set gets pushed off my head. Thirdly cables get in the way in scrub .
Now I just stick mine in pocket with volume turned down to a whisper and if mates just keep talking and irritating you with nonsense talk while your stalking then just sign off.
But I use the hand held and headset when spotlighting off the back of the ute to communicate with the driver via in car UHF radio. In winter the driver likes windows up to stop cold air and keeps out sound of muzzle blast as ear muffs block spoken commands (same with summer with Air Con and dust )
Best to stick with scheduled reporting times in case of emergencies during hunting (sprained ankles, sunstroke, snake bite etc) as well as turn on after a shot fired. Many years ago we were taught by Dept of Transport and Communications (DOTC) to listen for weak emergency signals on all channels at 3 minutes to the hour and every half hour. In fact this is still taught in the marine world. UHF emergency channel is Ch 5 (and 35 in duplex mode).
Handhelds are great when travelling with hunting buddies in several cars who may not have a UHF radio - just lend them one for the trip as not all areas in outback Aust have mobile phone coverage. Make sure you get the rechargeable kind (240v and 12v versions) with a spare battery or 2.
