I know two people with the EcoBoost and Towmax. Both are towing pretty good sized travel trailers and one a 24 foot power boat with two large outboards.
The trucks apparently do well and no power problems. But in towing with a gasoline powered truck, you will get about the same fuel economy when towing as if you were using a large bore v-8 of like power. Power comes from gasoline and you have to put a certain amount in the engine to get the power to pull the load. There may be a small difference in engine efficiency and a slight improvement in overall fuel economy, but not a lot. You can only do so much with the thermal efficiency of an engine. They were getting about 8 to 9 mpg.
Running empty, lots of power and better fuel economy...provided you keep you foot out of the throttle.
If I were to go to a smaller and bumper pull trailer, oor a small 5th wheel, I'd sure consider the EcoBoost.
ken