NHC250 is old, and while parts are still available at Cummins dealers, there aren't that many people trained to work on them anymore.
You can get more power out of an 8.3, easier.
The 8.3 is quieter, and gets better mileage.
I went from an M934 with NHC250, to an M923 with 8.3L... for the exact same use case.. 'tiny home on wheels'...
Yes, there's an added turbo for complexity, but the 8.3L is something most modern diesel techs can work on, and it's easy to rebuild if needed.
My fuel consumption on my M934 was ~4.5-5.5 MPG, no matter how I drove.
Many people report 8-9 MPG on their M923, but even if I only get 7 MPG, that's a 25%+ increase over the NCH250..
Might not sound like much, but imagine a 3K mile trip across country..
3,000 / 5 = 600 gallons = $3,000 @ 5$/gallon
3000/ 7 = 428.57 gallons = $2142.85
Nearly a thousand bucks saved.. in one trip.
I will say though, the NHC250 has a drone/sound, especially at idle, that I love, that you just don't hear these days... and I do miss with the 8.3L. The 8.3L is damn near silent in comparison.
I compare it to a Huey, in terms that you KNOW that sound, nothing else makes THAT sound, and if you hear it, you know exactly what it is without having to see it.