Our 2012 Wildcat came equipped with a Girrard tankless. We had a heck of a time getting it to work correctly. Our dealer work real closely with Girrard about our issues. Two things came to light. #1 due to the long run from the tank to the kitchen sink we could nearly fill the galley holding tank trying to get the water hot enough to wash dishes.
At the same time it was impossible to control the temp in the shower without scalding ourselves. Ultimately Girrard authorized a replacement to an upgraded modle. This one temperature overide setting allowing us the increase beyond the originial limits. (15-25 degree max increase
One thing to consider is they only heat the water to a fixed increase range beyond the temp of the incoming water. ie 60 degree water would only heat to 75 to 80 degrees resulting in very cool showers. WARNING!!
if the incoming water is colder, then the heated water is also cooler.
With the newer modle we are able to do what we need to comfortably take care of our needs. I understand there may be a 3rd generation tankless heater from Girrard that is even better than what we have.
I'll leave you with: Do your home work, see and test a working system in action if possible. Consider the impact on your other equipment (holding tanks) and then do whats best for you.