I take a few things out of Edmunds testing.
The 2.7 delivered better fuel mileage in mixed suburban driving than the V8. And as they note, that is with the auto start stop turned off.
In pure freeway driving, the numbers out of the two were similar, and that doesn't surprise me. Note that the gearing was different in the two trucks (3.73 behind the 2.7, 3.31 behind the V8) and the 2.7 also had the aero disadvantage of having the optional towing mirrors.
Last, I've always taken reported fuel economy numbers with a grain of salt. Seems it can be tough for an auto enthusiast to keep their foot out of it when power is on tap. Averaging right at 20 MPG on my 2.7 to date, and I'm not even trying...
The good news is all of us have options on what to buy that fits our needs.