I used the Portable Buddy for a couple years. It provided heat and is fairly inexpensive to purchase. But it operates very hot (fire and pet risk), emptied the little (expensive) bottles very quickly, and had a "smell". The heat it produces is both radiant and convected (it heats the air directly) which is nice, but I was never comfortable leaving it on overnight.
Last year, I "bit the bullet" (they are expensive) and switched to a Wave heater. Not too hot to touch (quickly), uses my on-board propane (cheaper to operate), seems to keep the cabin much dryer than the Buddy (I can't explain this, just my observation), has no "smell" what so ever, and very comfortable (radiant only) heat (air is heated indirectly by first heating objects in the trailer). After several experiments with a digital CO monitor running the heater in the completely closed up trailer, I am comfortable leaving it on overnight. Though I do make sure I have a window cracked open and the ceiling vent open.
For both of these heaters, you have to have both a window and vent open, but "so what". Winter camping requires ventilation no matter what the heat source to remove the moisture that people and pets exhale.
There are safety concerns with either heater though. Namely, running a gas (oxygen) consuming appliance that has the potential for generating CO in an enclosed space. So don't skimp on the ventilation. There is a heater, similar to the Wave heater, that exhausts combustion by=products outside (still uses cabin air for combustion), but do some research on it first.