What's available as to their budget? In the end, that's what it will come down to.
The TRBO model digrar mentioned (XPR 6550) goes for around 300 - 700 a pop. Then, it comes down to a few other considerations.
Gang Chargers - 1 centralized location where all radios are located when not in use and charged.
Single Unit Charger - If the radio is issued, assigned to the user and they are responsible for its control, and keeping it charged, either at their office or at home.
Batteries - Motorola OEM's are around 65 each.
Any other peripherals - ear pieces, hand mic's, mobile unit (Used as a base station)
Base station radio - Handheld or a mobile unit?
Antenna - Whether Vhf or Uhf for the base station (If used) and where it will be mounted (Think top of the building) and then, routing of the coax (How many feet of coax)
Try before you buy - There are several companies around your area you can consult with, rent their radios and systems first. See what works, what doesn't and go from there.
Shoot me a PM if you need further.