I have worked in shops for 30 years that have had both in floor and above floor heat. I prefer the in-floor over any other kind of heat. After the door has been opened and reclosed heat recovers much faster. If the floor gets wet it dries much quicker, also there is no cold spots in the building with in-floor heat. Your floor is a giant heating pad. All the new shops in our area are installing in floor heat.
Like it was mentioned in the one post before me. Above floor radiant heaters can be pretty hot if you're on top of a vehicle and just a few feet away from the heater. I don't think this would be good for your fire equipment either. Just my thought.