The heat strips and ceramic heaters will use a lot of electricity for the heat they generate. The heat pump is much more efficient but will only work down to about 40°. Both of the A/Cs on our unit are heat pumps and we have found they work very well. Whether they cost less than propane I am not sure, but they do eliminate runs to get propane tanks filled. In a S&B situation in Florida, the heat pumps are the most efficient and economical way to heat a home. I would imagine it would be the same for an RV. Since your unit is ducted it will definitely warm the entire unit better, again as long as the outside temp is higher than 40°.