If you are usually in mild weather, I'd save my money and use a ceramic heater. Except in really cold temps (lower thirties and under) we just use a Honeywell portable electric heater. It isn't a ceramic type but it does pretty well, even in our 34'. I have two rooftop A/C units, each with a heat strip, but my wife doesn't like the noise so we seldom use these for heat. I've never had a heat pump in the trailer. Our home had a heat pump until we switched to a high efficiency gas furnace a few years ago. We didn't like the residential unit.
The only problem with the ceramics or other portables is the limited circuit capacity of the trailer. For example, we usually shut the heater off when we are using a toaster. This is a minor inconvenience.
'92 Limited 34ft (now sold); '96 Dodge Cummins 4X2, 5speed