I've owned and used all systems except the hydronic heat. I've used that one on other people's boats. I'd say I have to agree with most of what everyone here says.
1. Hydronic heat is the safest, easiest, most efficient and DEFINATELY the most expensive. This is what I'd choose if I were to sail high latitudes year round and had the cash.
2. Diesel drip pot (dickenson) type. Second easiest, second safest. I have slept with these running at night, but don't really like to. I've also seen people get creative with copper tubing around the stack and a pump and make their own hydronic type system. These are a really good option all around IMHO and some of the models have a window to watch the flame.
3. Propane. Propane heat sucks unless you're a weekend sailor. We have a wall mounted propane stove currently and it will NOT really heat up the boat in modest cold. It also cooks through a heap of propane in doing so and finding a place to fill those heavy bottles is much more hassle than dealing with the other fuels.
4. Wood heat. Ahhhh.... I love wood heat. Much messier, less efficient lb for lb, more effort, less safe than diesel (arguably more or less safe than propane). The reward in romance is incalculable though. It's also a really nice dry heat and contrary to what dickenson says you can REALLY put our a lot of heat if you want to. I had the "cole stove" which is basically dickenson's solid fuel stove. It was nice because you could view the flame but it was not airtight
. This is a key point because it decreases your ability to control the flame and you can not easily extinguish the flame either. The only true efficient, safe and controllable stoves are airtight. I wouldn't sleep with my dickenson style wood stove burning, but I would with a controlled flame in an airtight stove. I'm currently looking for a wood stove for my new boat which is both airtight and has a window for viewing the flame. So far I haven't found any, though I may see if I can get this guy to make me one. Traditional Cast Iron Marine Stoves by Navigator Stove Works,Inc.
I tried EVERY type of fuel that you could possibly burn in my wood stove. I never did get pellets to burn very well, and try I did. Charcoal works fine but is messy. The best fuel by far, from my perspective, was the duraflame 2hr fire-logs. They burn cooler than wood (but plenty hot enough) and are consistant. I would cut a log in thirds and each third would burn 2 hours and make my 31ft boat 80-90deg. If you find them on sale they're dead cheap and since they're made of mostly wax they don't mind being stored in a wet bilge. Regular wood burned too hot for me, required much more sawing and re-adding of fuel and driftwood, while free and attractive has such a high salt content that unless you have a 316 stainless stove the salt and heat will soon put holes in your stove.
I absolutely want to pitch my propane stove overboard and go with wood. It's not entirely for rational reasons, but I'm wiling to put up with the extra effort for that nice dry, radiant, romantic heat. It's also a heck of a lot more fun to light than a webasto.
EDIT YIIPPPPPPPPEEEEEEEE!!!!!!! The awesome cast iron stove maker I referenced above is now making glass panels for his stoves!!! I[ve seen these stoves and they're fantastic! Some are even EPA certified (ie less soot) and you can even get drop-in cooking burners for them. Finally the wood stove I've been waiting for!!
Before next winter I will have a wood stove again. YAY!