I have to say that my Dickenson Newport (diesel) is a wonderful heater, throws and amazing amount of heat for the amount of
fuel burned, and because it draws air into the boat, it helps keep everything nice and dry as well as warm and cozy. Some people think that they smell however, and unless I have the air
fuel right they can smoke too (not enough air for complete combustion) but that being said mine is on its 6th year of faithful
service, and on a
Catalina 30 it throws enough heat that unless it's below 45°f you have to open things up so you don't and up just like the
Christmas turkey, and it rarely ever gets turned to high, but when it does you know it's cold (not more than in the
single digits)
On the other hand I have always liked the idea of solid fuel heaters but space is premium and the fuel takes up a mess of space otherwise I would have one, also with most solid fuel heaters, you have to be the one that feeds them and I am generally to lazy to be bothered.
Alcohol heaters ... I actively dislike them, there fuel if not very energy dense and bulkier and an alcohol fire isn't all together that warm (course I still wouldn't be sticking my hand in it)
Propane I actually like, my last boat had propane, but she wasn't pulling extra duty as my abode either, she had the propane version of the heater I have now, the heat produced was way more than adequate for a 25 footer, it was easier to light (no fiddling around with a piece of paper towel and a match, like I will be in,a few hours) and the viewing glass on the heater was nice added a nice cozy feel to the
cabin.
Electric heaters, I have a couple and I want to like them, and they do have their uses, but they do nothing to draw dry air into the boat, can not be used away from the dock (on most boats anyway) but if your not
living aboard and the boat is staying in the slip, and your just going to be around for a few hours, they are hard to beat (Although an electric ignition propane would probably come close)
Hydronic heaters and forced air heaters I am not that familiar with, I do know they have the option (mostly) to be controlled by a thermostat....
Hope, some or any of all that helps, but there are some really knowledgeable people here, someone here, not only probably has something but they can explain how and why it works too.