I was told second hand that the outdoor furnaces can be used with forced hot air as well, you just use a couple of heat exchangers to get the heat from the water to the air.
And in terms of efficiency, well, that's dependant on a huge number of factors.
You could certainly make the case that less cutting and spliting (even if done by hand) saves wasted energy, not to mention the actual wood saved in making fewer cuts. And because the heat from the furnace is distributed evenly in the house, there are fewer high gradients between the interior and exterior of the house and overall heat loss would be less than with a woodstove.
When you weigh how close the two really are, plus all the convenience factors you mentioned as well as the ability to heat water for water consumption, it really does make it an attractive idea. The one hold back for most woodstove users is probably just installation cost or space.