Range depends on a number of factors, below gives a very brief and basic description to help you decide which radio is best for you.

Environmental factors:

Terrain flat terrain will provide greater range than hilly terrain as the hills will block the signal from the radio.

Buildings buildings will degrade the range of the radio as the signal can’t pass thru a building as easy as it can thru open spaces.

Hills vs Water The best place to get the greatest range is to be standing on top of a hill with the other radio out on the water, this is because there is no obstructions in the way to degrade the range.

UHF vs VHF UHF is better if you are using the radios around buildings/ built up areas due to its short wave length as the signal moves out from the radio.

VHF is better in forest areas which are covered in pine as the VHF signal can penetrate thru the pollen build up better than UHF can.

Radio Factors:

Power basically put the more power the more range, this is because with more power the radio can put out a higher signal strength which can reach further.

Radio components going cheap is not always the best option, this is because to keep the radios cheap manufactures use more inferior parts which in turn lowers the range and performance as the parts in the radio are not designed to as a high quality. In other words choose which radio will best suit your needs carefully otherwise you can end up with a radio not performing as good as you hoped for.

Antenna  The higher DB gain an antenna has the greater range it can send the signal, also an external aerial will have much better performance than an internal aerial or one built into the radio.

As gain is increased the radiation gets compressed into a thinner pattern and reaches out further to the side. The more gain an antenna has the thinner the pattern becomes and the further the signal can travel. However a thinner radiation pattern may prevent strong signal reception when in the hills.

Low gain Antenna (2-4dBi) are good for hilly terrain but lack range on the flat.

Medium gain Antenna (5-7dBi) are good all round antenna which works well in both hilly and flat terrain.

High gain Antenna (8+dBi) are good in flat terrain but poor in hilly areas.