My last two trucks have been 4wd diesel with dual alternators and upfitter switches. I prefer to have the additional capacities rather than have to upgrade later (if even possible).
Whether you need a diesel or gasoline engine depends on your towing demands rather than what you're hauling. I would have been at the upper limits of a gasoline powered truck making the the more expensive diesel option a better choice.
If you are looking at maximum payload numbers, you should opt for the gasser with Ram transmission. In reality most of this weight is loading the front axle and the payload is different because the GVWR limits but the truck frame and axles can handle more. The Cummins diesel and Aisin transmission are both heavier than the previous setup reducing the paper payload.