Something for everyone.
We do not plan to boondock but once every blue moon. I for one really like the tankless water heater!
I have not used it using the on board water pump, but when hooked to city water it is fantastic IMO. If I take a 15 minute shower no big deal, wife comes behind me and takes another 15 minute shower shaving her legs then the grand child come in for another 15 minutes. We then wash dishes from breakfast and we have nice hot water the entire time.
If three more people wanted to shower no problem, the hot water keeps coming.
If water is being used elsewhere in the coach at the same time the water temp will vary in the shower, only negative I've seen. It does take a little time to get hot but so does our home, I guess I'm used to it.
We just got back from three nights at an RV resort, it was six showers, two nights cooking on the grill (I hook directly to the on board propane to grill), cooled the frig before the trip on propane, washed dishes etc. and I used less then 2 gallons of propane. *I* do not consider that an expense, I actually thought that was very good.
Don't get me wrong, for boondocking I can see where the tank heaters may be a benefit, for me though I'll stick with tankless.
Flame suit on