Val,
The bigger the fire box equates to more wood and longer burn times. Many stoves rated for larger spaces still need fed every 4 to 8 hrs no matter what in all honesty. It depends on the outside temps and the quality or mix of wood you are burning. I do like burning wood and it is a cheap heat source. I also like to state the truth as to not mislead with false high hopes. Some single stoves can produce long burn times but many of these are stated under ideal and not real world actual average use. Fishing tales.
I will put it this way. Many pellet burners are former wood slaves. Why?
As for the little stacks of foreign wood.... It does not require much to heat a 10' x 5' box, home, sleeping tube or whatever it is they call their palaces. Many in other areas of the world can not sustain much more than a tent and an old bicycle. People in other parts are fortunate and many take it for granted until it starts beating up the good old wallet. There are granolas living in the US in straw and mud huts heating with rocket stoves also. Google rocket mass heaters. Neat concept but only half way practical for very small domains.
A $4,000 tiny stove and pushing it for use on a boat is just ridiculous. Fire and water do not mix well IMO. Neither does fire and a rocking boat made of combustibles. One good thing. It won't burn long.
Wood burners come in all sizes and like pellet stoves I tend to go bigger than the rating if you want a shot at them actually heating when you need them to comfortably. My little Acorn stove is small and I caught it about 8 or so years ago at TSC on a spring sale for about $99 if I recall correctly. It's good for one larger room not often used but will heat it up well if fed. Think it's rated for 1,100 SQ FT. I do an area of 800 SQ FT. At times that is a major workout for that small wood stove. If I had to keep that area warm all winter it would have a much larger stove throttled down to slow burns.