While diesel engines and turbocharged engines both have great
high-torque@low-rpm characteristics, you also might look at
acquisition costs, operation costs, and brand reliability.
When my wife wanted me to get a tow vehicle that would pull
the next size larger trailer (16ft/17ft), I seriously considered a
diesel tow vehicle. (My son has two VW Jetta TDI vehicles [one
sedan and one wagon] and a larger RAM diesel truck that he
uses to pull heavy horse/farm trailers.)
For multiple brands, they wanted additional money for the
diesel engine option on a new purchase (i.e. higher acquisition
With the current cost difference in diesel fuel, a similar 25 mpg
for both gas and diesel vehicles usually results in a higher cost/mile
for the diesel vehicle.
With my Ford Ecoboost 2.0L, I usually burn premium while
towing (the Ford owners manual actually says to do that) and
mid-grade or regular for for around town driving.
For a true towing fuel cost comparison, I guess you would have
to look at the price difference between diesel fuel and premium
gasoline for those towing miles.
Just my 2 cents worth .....
As always, YMMV.