I am on my second 3.5L and have had really good luck with them both. I agree with Fish-r in both the 3.5 and 5.0 are good. My dad has the 5.0. The things I have noticed between the two is my 3.5 would shift a lot less when pulling a 20 foot fiberglass boat than my dads 5.0, but his seems to get a bit better mileage. I recently took my 3.5L on a hunting trip to Illinois and got 19 mpg while driving 75 most of time. That is the best I have done. It seems to get about 11 when pulling a boat or when pulling a trailer with atv on it. The power and torque out of that thing are really awesome tho!! My brother has the 2.7 and likes it, but he doesn't really have the need to pull anything. If you are gonna pull, I would be safe and go with the 3.5 if you decide ecoboost is best for you. Good luck