The answer depends on a few things... GENERALLY (not always)
IF you are paying for it, Propane gets you more heat per dollar than Electric.
IF, however, Electric is "Included" well, then Cost per KWY=ZERO and it is kind of hard to beat that price.
HOWEVER.. If your in a Class A (or trailer) WIth "Heated tank compartment(s)" then it is very likely the Heat provided said compartments is courtesy of the furnace. And if you are using electric space heaters.. That will not work. (So i added heat to the bays from an electric source as well) Even my water hose and pressure regulator are heated, As is the park water supply near my rig (100 watts of heat in that area, under a bag, Nice and toasty inside the bag)
However if it gets cold enough (11) The electric heat in the basement.. NOT enough Though I may some day fix that by re-positioning a few elements.