You lost me at "towing 22.5k lbs over 8k feet at 65 mph" do you mean grossing 22.5k? Either way I have a hard time believing the V10 is cresting 8k feet at that speed.
I think the gasser 3/4t+ make sense for some and if it works for you, thats great. I'd be curious to actually run the numbers and see what's cheaper. I think that you're really only winning at purchase price assuming you're picking the truck up cheap. Towing that kind of wieght, you're getting absolutely abysmal fuel mileage.
There are quite a few 6.7 ps and cummins trucks at 400k+ miles. I'd be pretty shocked if the V10 lasted that long towing that kind of wieght.
Again, more speculation. Cam phasers seem to be the first to go out on either engine. Some people even reporting it sooner on the 5.0. Maybe because it's higher rpm nature?
They both seem to have very few fluke failures before 75k, some failures before 150k and typically need cam phasers before 200k. I was told by another member that cam phaser job is $3500. I don't think that's horrible for 200k miles on a newer vehicle. Much better than an entire new Hemi or 5.3 like the other brands seem to need.
I have yet to really read about many problems with the turbos themselves going out prematurely. They also aren't all that much either depending on what route you go.
I recommend this to everyone