I'd go with the 5.0 if I were you for the amount you wanna tow and like some have said the mpg isn't that big a difference between the 2. I'd also suggest at least 3.55 gears. 3.73 would be best but not entirely necessary.
For myself, I went with the ecoboost because I planned/plan on getting a larger tt and a landscape trailer and running my own landscape business next year. Plus I like the turbo whistle lol