I have no experience with the newer trucks, it just seems that the general feeling on Dodge/Ford message boards is that the newer ones aren't doing as well. BTW, many 07 Dodges have the 5.9 which is the same as yours and mine (03-07)
I'm not arguing to be an ass, I am arguing because you are issuing blanket statements based on very limited experience and even more limited knowledge. If you are going to call people an idiot for considering something, you should bring the tech to back it up.
I would be 100% comfortable hooking the trailer mentioned up to a gasser truck and towing anywhere. I have towed trailers this size before with gasser trucks. I spent 7 years as a construction manager for a company that built and remodeled hotels across the country. While not all knowing, I do have close to 100,000 miles of towing experience, with various sized (and overloaded) trailers, all towed with gasser trucks (Ford 460's usually)
Those trucks did fine, for 100,000's of miles with no adverse wear and tear and no safety issues.
Any engine with 600lbs of torque is going to tow better than an engine with 400lbs. Especially if said torque is at 2000rpm. But, there have been big 40-50' trailers long before there were diesel pickup trucks with 600lbs of torque.
My opinion agrees with yours, a diesel would tow that sized trailer easier and likely with better mileage than a gasser. But, depending on each persons situation, a gasser would do just as adequate of a job getting the trailer to the destination, and if depending on the mileage towed, the gasser might still be cheaper overall. Every one's opinion may vary and that is fine. But, calling someone "daft" or an "idiot" because they suggest, based on their experience, that a gasser would do an adequate job on that trailer is, well, daft, or idiotic.
This is the wrong message board for this, but I (for one) would appreciate some tech being brought to the table to back up your statements.
Obviously not an Official SEB opinion :)