Well yes and no. For what most people pull....a average size travel trailer or boat, most would never tell the difference in power.
I know a guy that leases new F250's every 2 years. He pulls a fifth wheel travel trailer with a boat on a trailer behind it. He goes from Sault Ste. Marie to White River Ontario all the time, and it's nothing but hills.
He got tired of the cost of maintenance with the 6.7 Powerstroke so he just got himself a 7.3 gasser and he said he puts the exact same gallons in every time he fills up pulling the trailers up there that his diesel did.
And the owner of my local welding shop got a new Chev dually with the big gas engine in it. He has a welding machine in the back and full length tool boxes on both sides of the box rails, plus his torches and bottles.
He showed me his dash display and gas receipts and he's getting 20 MPG on the highway.
I never got that with my Powerstrokes....not since the old 7.3 Powerstroke.