Motorola xtnid
But it depends on what you want for the best
The pmr system is restricted on the maximum output of the aerial, so unless it's cheaply made or more importantly has a lesser aerial then there is little in it with regard to range, the environment is core to that.
Want it to last all day with regular transmission, then you need something that you can swap batteries easily with (or just have lots of spare radios)
Specific chargeable batteries for the radio will work best, but to get spare will work out expensive
Choose one that you can take the battery pack out and replace with standard batteries then you can stock up on normal or chargeable batteries to swap during the day
Want convenience of channel switching then use an xtnid and programme all the channels/sub frequencies you intend to use.
If you have multiple ones in the team then get a programming cable and software. Then programme them all in seconds
The disadvantage of the xtnid is price. But pay attention to the forums and bargains pop up - see one around £40 and snap it up
http://p8ntballer-forums.com/threads/comms-on-the-field.158461/#post-1433942
http://p8ntballer-forums.com/threads/radios-walkie-talkies.168498/#post-1534092