The V10 Fords have about 360 HP in the trucks, while the 5.4L V8 has the same size pistons and stroke length with only 300 HP.
The difference is only your going up the mountain pass is about 10 MPH slower in the smaller engine truck. You will still get there, the radiator is much larger than the F-150 so it can put out all 300 HP more time before getting warm.
For reference my 460" V8 7.5L only has 225 factory horsepower, so it likely is beat by both engines. And I have a 20,000 GCVW.
Fred.