There is no economically rational reason to purchase a KK. It performs well, but it also has limitations (limited grill space, access, and "degree of indirect heat" in comparison to some of the insulated vault or offset cookers). The heat retention and fuel economy (read potential cook duration per load) are incredible.
What is remarkable about the KK (and perhaps other like ceramic ovens) is that you can smoke your Tri Tip at 235F, and in in a few moments, execute a reverse sear at 500F; then finish a pizza in 6 minutes at 900F. When you shut it down, it will hold temperature with very little loss for hours.
If I were in the market to make such an irrational purchase, I would get the 32"; otherwise you will have to do "rack workarounds" when doing big rib and simultaneous pot-of-beans cooks.
BTW, the materials used on the KK are derived from the space shuttle program and related industries--and do not come cheap!