Opinions needed on Tow truck - Diesel or Gas?

[gemleeus]

my boss and i went on a fishing trip to fla. on the way down, pulling a 20ft grady white boat w/ late 90's 454 dually. the boss got so tired of upshifting and downshifting, we stopped in a dealer in ala. and he bought a new 3500 diesel dually. at first the truck was a little herky-jerky with the boat, but once the trucks computer learned the boat was back there it was like driving any other truck, and sometimes almost forgetting the boat was back there. the truck pulled it very smoothly and would downshift automatically when coming to a stop making using the brakes hardly none at all. myself not having to much experience with pulling with a truck was very impressed. the truck pulled the boat effortlessly. the boat i know weighed over 12k. lbs. probably much more. 3500 dually, duramax w/ allison trans.