Wife doesn’t have to fuel over at the big truck islands. You or her can fuel with the autos only on the end pump commonly and only every 600 miles instead of 400 miles. Lots of Wyomins due to landscape put on more than 15k annually with someplaces taking 90 miles between fuel stations. But I agree with the 15k being one useable guideline.
Not everybody is a hot rodder like you Shiner. If it’s easily fast enough for DW she might care more about the fuel economy. Extra horsepower only means something if she feels the need. Both have plenty of pulling power for his trailer in fact the Pentastar would with the 3.55. Have her drive all three see what she likes the most.