I paid the extra $20-$30 bucks or so and got the Mr Heater unit with the two burners and the built in fan. You can use it on the one burner setting and turn it to low for smaller tents or warmer days - or you can crank both burners on high and ice fish in your underwear at minus 30.
It keeps my Big Clam tent (12 foot x 12 foot hexagon) toasty warm.
The fan circulates air and, in my opinion, makes the tent more comfortable as there are no cold spots. It's not great when your legs are on fire and your bum is frozen - I just set the heater in the far corner and turn it on with the fan and I'm never scooping ice out of the holes and quite comfortable with even heat.
I can't think of a better heater that I've ever owned.
I run an adapter hose, inline filter, to a 11 lb propane tank that lasts me 4-5 trips Just to avoid the cost and nuisance of the small 1lb tanks.
The link below has the same model as mine ..... worth every penny ....
http://www.jccayer.com/Mr-Heater-MH1...re-feet/p/5699