Back to power vs fuel efficiency...
Our current 2017 F350 DRW 4x4 lists 440 HP & 960 #pounds of torque...yet it is more fuel efficient than either of our prior F450 and F250 tow vehicles. I think the new vehicles can satisfy EITHER the need for power or fuel efficiency. It all depends on how heavy the right foot of the operator behind the wheel!
We are towing over 27,000 GCWR; if I keep the speed at 65 mph or less, we average a tad over 10 mpg on a long trip. I think that is spectacular based on prior tow vehicles. And it would be even better if I were willing to drop down to 55 mph and not race that guy in a Dodge to the top of the next hill
The point is, the new tow vehicles give you some choice - you get to decide if you want to burn up the road (and a lot of fuel) or relax and spend extra time to cut your fuel costs. That's an option for us all that we commonly didn't have a few years (and vehicles) ago.