I've seen track conversions for the Polaris Ranger and the Kubota UTV, both with the intent of using them for light duty trail grooming. The brief reviews I've seen would lead me to the heaviest, largest of the Kubota UTVs if you want to do any sort of trail grooming. If you just want to do trail riding with a tracked machine then either one of them would work, but both will be very slow with tracks (as will be any other track machine).
I know several people with UTVs and all of them love them. As Brian wrote in the first reply, for work, the UTV is the answer. I own a light duty Yamaha unit (no tracks on that) and it can't even compare to the UTV, then again, I didn't buy mine for heavy work since I've got other equipment to do that.