Lantley summed it up in one succinct statement. End of discussion. 
I can take a new 6.0, 4.10 Chevy and it’ll sht all over itself pulling an 8-10k flatbed trailer between here and Spokane. Truck will get 7mpg, shift 1,234 times and have to stop in Moses lake for gas. 
I can take my old Dodge 5.9, same size fuel tank. 4500lb 12’x8’ billboard in the bed (camper) and a 6500lb boat behind it. I will downshift it exactly once for necessity to 5th gear coming out of Vantage. Truck will pull 6th but egts get too high. And have enough fuel to get into Montana a little ways. 
You decide which you prefer.