The Espar was by far the most efficient but I liked the Wallas over the others as it provides a cooking source as well. I would not go that route if you're sailing in warm, tropical waters as it takes 10 minutes to boil a pot of water and the boat is warmed while you're waiting.

I forgot you had a diesel in that thing; makes a bus heater an option. I've never used one but don't see why it wouldn't work okay. I would imagine it keeps blowing warm air for another half hour after engine shutdown.