Wheelbase is probably the most important factor in towing that people seem to overlook. No matter the weight, when you start getting trailers that are longer and taller, the foundation of your tow vehicle needs to get bigger. While it may tow pretty well now, you pull the same trailer with your current truck and then a truck with a longer wheelbase down 71, you would notice a difference. It's not that one is bad, especially when you are into HD trucks, but if he isn't going to daily drive it, then he should go for the longest wheelbase he can get to ensure he has the best tow vehicle he can get.
As for turning radius, tell me about it. I learned to drive in a 1989 Chevy 3500 Western Hauler Crew Cab Dually. Before my parents let me take my driving test I had to hook up the horse trailer, tow it, park it, and unhook it.