Yes i agree on the free gas.I just hauled a car in with a half a tank.That is reason i was thinking about getting a v10.But on the trailer gas would be a pain to drain.If i had a lift then i would drain a crap ton of gas.
Yes diesel parts are expensive but last a whole lot longer.So when your gas truck reaches 300k you have done had the motor rebuilt or a new motor put in and how many other gas failures have happened who knows.
Also diesel are built for heavy towing so if you tow alot a diesel is for you and it will get 5-10 more mpgs towing than that gas truck will.