I have the older style non-electric vented furnace and find it to be preferable over the new (electric valve body+fan) units. One of the problems with the new(er) style units is that, if the pilot flame blows out, the furnace will still turn on, fan blowing, but all it's doing is moving cold air around and will do so NON_STOP!! That can lead to a severely depleted battery in the morn and an EXTREMELY cold living area, since the furnace then effectively acts like a heat exchanger and sucks it all out. The same thing happens if you run out of propane with the furnace turned on.
What I did is to add a thermocouple (normally open) to mine with a computer fan hooked up to it. Thus, when the burn chamber reaches a certain temp, the thermocouple closes and the fan turns on, blowing air past the burn chamber and also increasing efficiency. ..Willy.