I examined this under a microscope before purchasing both. While a diesel dually is of course the ultimate tow vehicle, I don't need or want the trouble of a diesel or the inconvenience of a dually. I like parking my truck in the garage during winter, I don't want to plug it into a block heater and I don't like searching for parking spots that are big enough at the mall. Also, diesel is a cost and maintenance headache I don't need. The new 2017 Ford F250 has a beefier box frame, upgraded heavy duty chassis/suspension components, heavier brakes and is still lighter due to the aluminum body. I've added all of the towing upgrades and with a 4.30 rear, it is rated at 15,300 for a fifth wheel, making it suitable for my needs from a ratings standpoint. With the addition of Timbrens or Air Lifts, I don't see any reason why this thing won't tow straight and level without killing itself. I also surveyed some towing professionals and they agreed that my power pick will do the job. The service manager at my RV dealer has been towing RV's (and driving semi's) for 35 years and he said he'd put his family in this rig. I also talked to a "transporter" who, while he did say that a diesel dually was his preferred choice, has towed many rigs with a single wheel gas without problems.
I'm sure I'll have a pang of regret when climbing the Rockies, but then again, I'm retired and in no particular hurry. Regarding keeping the rig in a straight line, I've towed large boats and trailers before using a single without issue and as I mentioned, the new Ford is a far more stable platform than previous models. If I had my druthers, I'd be towing a 40+ ft toy hauler with a Ford F450 full time. Unfortunately, the boss has indicated that i can't have my druthers, so compromise has become the better part of valor. In other words, what I've got here pleases my wife.