I have a Webasto. They are expensive, but have an awesome dry heat , and use very little fuel (my 5 gallon diesel tank usually only needs to be filled up once a year, used 3-4 times a month in winter). Power consumption is extremely minimal too, can run all night without draining the battery.
The planar are much more reasonably priced, and I have heard good things from people who have installed one.
I have used propane heaters and find the exhaust and humidity most unpleasant...I'd rather bundle up, and do without personally.