We have both engines in our work fleet. MPG's are all about your gear ratio. 3.31's in our Ecoboosts have done about 1 MPG better than 3.31's in the 5.0. Since you can get 3.15's in the EB, it will do even better. The low RPM torque of the EB allows it to handle the 3.15's with power to spare. For towing, you can't beat the EB. Even with my 3.15's its rated to tow 8800 lbs. I've had a 7000 lb trailer behind it several times and the power is unbelievable. RPM's rarely get above 2000 even on hills. The 5.0 is a great engine and it tows fine too but it is working harder to do it. BTW, the EB 3.15 truck I drive everyday has about 4000 mostly highway miles on it and it has averaged 20.9 mpg over those miles.