I am new to the whole thought of heat on a boat, as my old boat did not have it, but I only lived on it during the summer a spent winters at my parents house. My last house we had oil heat, but also with a wood stove. Wood if you have a source for it is actually much cheaper, normally free. Here in the North East you can get enough wood delivered, cut and split, for a whole season for around $200. I don't see doing that with diesel . Storage could be an issue for a boat but you should be able to rent a bit of space in the boat yard. I don't really plan on sailing once heating season arrives, as it will be iced up anyway. I was thinking that both an diesel and a solid fuel heater combo makes sense. You can run the wood when you are on board, and have the diesel as an option to keep the boat from freezing while at work.
To me in the day and age of uncertainty about oil prices and availability having options for heating works better for me. But I may just be a bit paranoid. Of course I am planning on making my own bio diesel for the boat in the summer.