I'll agree with your Dad that you don't need a diesel to tow the weights you mentioned and amount of towing you'll do. If you go with 3.4T I think the only gears are 4.10 gears with the 6L 6 spd auto. Towing capacity of 14,800 lb. Gas mileage will usually be under 15 MPG.
The new 1.2T has towing up to 12,800 and with the 5.3L would get much better mileage as a daily driver (16 city, and up to 22 highway). Also can get 3.42 or 3.73 gears.
I had a 1/2T 5.3L 4 spd auto and 3.73 gears and it towed fine. But once I bought trailers over my 12K tow rating I swapped it in for my current 3/4T CC 4x4 6.0L 6 spd auto and 4.10's
