My daughter has a tankless system that they installed about 12 years ago and they've been pretty happy with it. But it's a high BTU system for their small 4 br. house. The ambient water temp is not so cold so the amount of heating that has to be done is well within the capacity of their heater. The heater in my sister-in-law's apartment works well but they have the flow rate set at the minimum and the temp at max. Like my daughters, they have a starting temp that is not too cold.
I looked into a tankless system when I lived in northern NJ and decide against it because in the winter the starting water temp was just too cold for all but the most costly heaters.
For us, we're sticking with our Suburban 6 gal for our Pod. We hardly heat water anyway and it is more than adequate for our needs. The extra weight is of no consequence in our already light trailer.