My sales guy that sold me my ’10 F150 with the last 5.4 has been telling me that the ecoboost in the F150 was never designed specifically for mpg. It was designed for power AND mileage.
A motor with comparable power would never be able to get 20+ mpg.
I know for a fact that the 5.0 gets very similar mpg as the ecoboost, but the ecoboost has much more torque and is more fun tor drive.
Simply put, you can’t really go wrong with either, just don’t expect big savings at the pump with the ecoboost.
Focus more on the rear end gear ratio if you want better mileage. You have 3 options, 3:31, 3:55 and 3:73. they offer these for a reason and I am always shocked when I ask someone what gear they have and they don’t know.