[nvmyss]

Having owned both a 2001 HD Crew with the 6.0 tuner, cold air and headers.
And a 06 5.9 Dodge Cummins that I've changed from stock to mild modded., here are my 2 cents.

I've towed with both and same weighs and distances. The Diesel is hands down my choice, I will never go back to a gas truck. (unless it's a "fun truck" --one that is not used as a truck. A truck is for hauling stuff and treating it rough)I have towed 24' enclosed trailers load with a few thousand lbs. and open trailers with little weight.

The torque of the diesel will shine compared to the gas in a few areas. The ones that come to mind are mileage, hills (both up and down) and price to increase power.

Each brand of diesel has its draw backs.
Maintenance and fixing the "weak link" will cost more than a gas initially but if you’re going to own for a long time it is worth it.

The 6.0 I got 12mpg no matter what, hills knocked speed and mpg down when hauling the enclosed. The open trailer was better but hills still sucked with weight.

The diesel I can keep going @ 75mph and still pull 18mpg on hills, flat land I and go back over 20, this is with a loaded enclosed trailer.