When you get down to the point of having it that close I think it makes better sense to just get more truck, but that's just me. The difference between the towing and hauling performance is dramatic, while the difference between daily driving or highway cruising comfort is minimal to non-existent.
I just did a 650 mile highway trip without my trailer and the truck was really comfortable I averaged 22.4 MPG. The trip involved lots of mountains so it wasn't ideal from a fuel economy standpoint, although my speeds were limited to about 65 mph so that helped.