Circulation feature is nice, but I'm not sure it is worth hassle of the extra piping you will need to do it correctly. We have a circulating model, but had to use existing pipes since we have a lot of concrete walls and 2nd floor deck is concrete as well. When on circulation it was never as good as what we thought it would be.
We go through the same amount of propane with 4 people on the tankless as we used to go through with 2 people on the tank heater, so they are pretty dammed efficient, and with two teenage boys taking long soapy showers, we never run out of hot water.
That being said, one could always up the wrap insulation on the tank and get that thing pretty close without all of the tankless issues and costs, even if you get a larger tank to ensure a large supply.
You will also need to to do the the scale cleaning every couple of years on the tankless to prolong the life of the unit. i did not do that on my first tankless unit and it gave out after 15 years.
There are subs that do nothing but install tankless, they can tell you what you need.
Our tankless is inside and I always wanted it to be outside, until last winter.