Not if you speak Spanish or Portugese :)
Parts are substantially cheaper than OEM Isuzu in my experience
I can't speak to thermal efficiency, and don't question that on paper its not as efficient as a 4bd1t, but it will move a 3tonne F250 along at around 11l/100km. I can't imagine a 4bd1t would be appreciably better in such an application.
I'm sure you can beat the power listed with a 4bd1t, but not from the factory. And if you start going in that direction... well...
https://www.youtube.com/watch?v=7Ar15Zfyl5E