I to had this same issue and read all the various feedbacks prior to purchase of a tow vehicle. Based on the actual towing I have planned I decided on a F250 V10.
We took our first towing vacation this winter and traveled 7,000 miles towing a 2011 37' Big Country. Yes, I was passed by every diesel on the road and there r a lot of em' but I'm retired and didn't mind going a little slower up big climbs. But if I were planning on constant trips the diesel would be the way to go. The newer diesel engines don't get the milage like the older ones but if you r worried about the money issue RVing ain't a good future for u. As a gentleman told me many years ago when I inquired about gas milage on his Jag, if u can't afford the gas you can't afford the car. Other than the up hill speed the V10 was great for me.