I don't know much about the emission-era ISCs, they seem to have a fairly decent rep with the motorhome community. I do know that they have Common Rail injection as opposed to the older CAPS motors. The turbo is also a variable vane design so its more complex. It wouldn't have DEF, not sure if it would have an EGR cooler or not.
It's a wet sleeve design so it can be rebuilt inside the bus which cuts down on that cost a bit. Overall the 8.3 is one of if not the best motor you can get in a skoolie. Power wise there isn't really anything that can compete with it.