Are we now judging the inherent goodness of vehicle based on how it burns? What a waste of mental effort and time with such a discussion.
On topic - What CR says on the matter is that in general ecoboost engines don't do so well comparatively, but the 3.5EB gets within 1 mpg of the newer GM 5.3DI engine, while performing very similar. CR strangely has the only test I have seen where the 5.3 slightly edges out the 3.5EB, but they do complain about the lack of response from the GM, which is one way it achieves better mileage, I believe GM euphemistically calls it "electronic coaching".
