I guess my question would be why you want to spend literally thousands of dollars for an item that you will never recoup the cost? It just won't happen with a tankless. And you will have to take that device apart and clean it of calcium buildup in the heating compartment to keep it running as efficient as the day it was installed. Along with having a service tech on a short rope to help you spend 100's on that unit when things go wrong.
On one of these forums I had a comeback that, "Do you know how expensive square footage is in California is?" when I made a statement that the square footage you gain is a bad reason to install a tankless over a tank water heater. I don't buy that lame excuse. Closet space is closet space, buy ventilated shelving and work around your situations.
I mean if you want to be in the in crowd and have something that only a select few have in your area, go for it. Wave of future designs have their setbacks in many ways, give it 20 years and they might be price competitive to the tank water heaters.
Remember, history always repeats itself; Remember the old RUUD water heaters that worked solely off pressure? Instant hot water water, some are still working today. Huge coil of copper piping inside the cast iron heater and when there was a fluctuation of pressure the heater kicked on and there is your hot water.
If you go forward with this, go with a 9-12 gpm flow tankless, especially if you have any square footage to the house you have to mention of. GOOD LUCK