I have a Webasto gasoline heater and I love it. I didn't want the extra hassle of needing another fuel source since I was already carrying gasoline for the promaster engine. That said, if I already have a working propane heater and propane system I am not sure I would go through the trouble to change.
Tying into the fuel system is the easiest part of the installation, there is a fitting that clips onto a spare fitting on the fuel tank, you open the fuel access, remove a cap, and replace the cap with the fitting. Then attach the fuel line to the fitting.
Cutting the hole in the floor and getting everything attached from underneath is the harder part. I cut the hole in my driveway and then installed the heater later since I ran out of time for my build. I installed it in the parking lot of a mechanic shop (I rented a couple hours on a lift and they didn't show up, so I used their parking lot and saved my money, but it was cold and not fun).
I was adamant I did not want propane. I don't know if I feel as strongly about it after the fact.