My sister is really happy with her Ecoboost 3.5L. It is rated to tow around 10,000 pounds. You have to get a particular model to get the max towing, and max capacity, and max GVWR. Not every 3.5L is rated to tow 11,200 pounds.
I was reading the new 2015 towing guide, and the 2.7" Ecoboost in the F-150 can tow a larger load than the 3.5L! This is due to a 500 pound higher GCVWR and probably a 300 pound lighter GVW. So overall the curb weight + trailer weight is higher on a lighter F-150 than the heavier 3.5L Ecoboost, with the highest GVWR and highest tow package.
Good Luck,
Fred.