The Ford vs Merc comparison isn't valid because the two products are designed to meet MUCH different goals. The Ford engine is a work truck motor. It's designed to provide low end power, be used to tow/haul stuff (ie long runs at higher power loads). It was NOT designed with a cost is no object budget. I wouldn't be surprised if it returned almost the same mileage as the Benz despite being in a very large truck.
Yes, it hardly represents state of the art in diesels but it, like the tractor, was designed to meet a much different goal. Comparing such dissimilar motors says more about a lack of understanding of engineering design objectives than it does about the products being compared. Kind of like saying an F1 car is better than a Civic. Well that depends on the design goals.