I've been using UTM for purely pragmatic reasons. My Blazer 12 is one digit shy of a precise waypoint in Lat/Lon . UTM gets me closer, but it's tricky for puzzle caches, switching back and forth in the field. Fortunately, a new Meridian Gold is on the way, so I doubt if I'll be using UTM (or the good old Blazer) as often in the future.