Your really asking about a difference of 900#. That would be negligent in mpg. It's normally more about aerodynamics. Tow the pickup you are most comfortable with and meets your other needs.
In my semi empty to 45,000# in the box is normally less than a 0.4 mpg reduction on the same route. Terrain and speed have a larger effect. So I doubt you'd see any difference.
As for performance, 900# difference on a 28,000# vehicle is like asking if I should dump 110 gallons from your tanks before climbing a hill.