I have several heaters because I don't believe in the one size fits all.
I have a Sportcat which I use on nice days to dry my hands and take the chill out of the air.
Some people like this style.
I like this one, because I can heat up lunch by setting my sandwich on some tinfoil on top.
For 80 to 90 percent of my fishing I have the regular buddy heater.
And for the real, real cold days I have the Big Buddy heater, which takes two propane tanks, (or a hose to a large tank)
I guess you could just get the Big Buddy heater, and run it on Low. It would need to be a very nasty day when a Big Buddy heater couldn't heat a one man shack.
I have the Clam Voyager, and It gets it nice enough to fish without a jacket.
It's real nice not having to scoop ice from the holes, but it really is a pain to go check the tip ups.
Hope this helps,
Wiener