my 3.7 V6 tows fine, does exactly what i want it to do, i can run down the highway in 6th gear with a loaded trailer and still get 12mpg or better.... in the mountains pulling my enclosed car hauler and my Turbo mustang, my v6 F-150 pulls better than my 4.6 Expedition ever did....my truck has a 7,000 rpm redline..towing o never see it nor do i see constantly running at 5,000 rpm like some say either.... if you keep your towing weight realistic you wont have to rev the hell out of your smaller motor...
at the end of the day, if your tow rig does what you want it to do, it doesnt matter what anyone else thinks.... its 2014 and it doesnt take a large displacement motor to tow anymore.....new more efficient motors make more power and do it with better fuel economy.. we can crunch numbers all day long and argue what is better... yes, a diesel would be the all around better choice for towing but im sorry, i dont need it for my 4800lb TT....
if you like your truck, thats all that matters....