As far as tail boom colour goes, would concur that a dark tail is a must for Police or lots of hovering operations, whether TM or PW. It's the long hovering that cooks the tail - a nearby Air Ambulance (all Yellow) keeps a nice shiny tail as they just go from A-B & the tailboom stays out of the dirty airflow!
TM is definitely cleaner. Wipe with your finger in the exhaustpipe and you will see the difference! That has nothing to do with the flightprofile ( hovering operation ). Maybe the Air Ambulance use their time off for cleaning their machine....
skadi