I can relate a little since we've used a '99 F-250 PSD, 6spd. for farm towing duty for years, this past year dad got a '10 3500 cab-chassis Dodge, 6.7L, 6pd. He's a die hard manual transmission guy (as am I) and Dodge is the only choice still left in that market.
Anyways, a few observations on the new truck vs the old. The dodge definitely handles big trailers easier. Dually, heavier springs, better brakes, etc are all nice for towing. As far as power goes, it definitely has more power than the 7.3, but it is less useable IMO. If you get the right gear and right speed it will put an 18K trailer up hills pretty quick. BUT, the power range is very limited. Torque below 2,000rpms is non-existent, and it red-lines just a little over 3,000rpms, so there isn't much to work with. Wouldn't be a problem if it had 9+ gears, but as it is it's not optimal. Off-idle torque is very poor compared to the 7.3, with the dodge if you don't give it some throttle when you are trying to get a load moving it will stall out, not the case with the ford. Fuel mileage is about 10mpg for both when towing about 15-18K.
I'm not bashing the dodge, it's a great truck and tows much better than the old ford. However, I think these new 'high power' diesels are way over-rated. Sure it makes huge HP and Torque numbers, but it's in a very limited rpm range. Heck, it feels like my old gas powered F-250 (460) has more low end torque. Maybe that's why they've all gone to automatics nowadays, to better use the peaky power, IDK.
Personally if I were buying a new truck it'd have a gas engine, ten years ago I'd have gotten a diesel.
