I have a Coleman Hot Water on Demand portable hot water heater and we love it...used it endlessly even when we did our huge family camping trip last summer. It will save you on the propane and only heats when you need it. We have new TT that we bought Feb 25, this year and it has the 6 gallon hot water tank. Chances are we will still continue to use the Coleman for most of the day to day stuff and reserve the hot water in the trailer for washing up since we boondock most of the time
No experience with a tankless system on our motorhome, but we do have the tankless system at our permanent home and we have 10+ years of satisfaction. Congratulations on your pending purchase and welcome to the JOF!
Thanks everyone for their input and links. I did a lot of reading and decided to not go the tankless route. The main issue seemed to be temp of the incoming water and adjusting the furnace to compensate.