I checked into all sorts of options for our Safari. The catalytic heaters put out a lot of moisture, and you have to have a window and a roof vent cracked. Lots of people use them and like them, but I know I couldn't sleep with one going- afraid I wouldn't wake up.
I was setting ours up for extended boondocking, so I found one of the old radiator-type LP heaters. It pulls in combustion air from the outside, and exhausts outside as well, and uses no electricity. It kept our 22' at 72 degrees when it was 34 outside. Found it on ebay, and checked it out thoroughly before trusting it- it's about the same vintage as our '65.
There are modern vented heaters made, I think by Empire- maybe somebody will chime in that knows more about them. Here's a link:
Empire Comfort Systems
Couldn't find any info about using them in an RV on their site.
If you're not worried about battery consumption, then maybe ducted is the way to go, as it'll throw heat at the tanks, too. I just hate depleting the batteries in a night when I'm unplugged.