From what I've read the Ecoboost gets a lot less "eco" when you add wider/taller tires - supposedly it's more sensitive than a 5.0 with the same changes. The tires probably cause the turbos to spool up sooner than with lighter/skinnier tires. Either way, I'd get the EB every time.
I switched from an f150 to a Yukon partly because of the increased fuel economy and it gets the same as my old 5.4 (12/16).
This post was edited on 3/8 at 1:21 pm