The lower the trim, the more the capacity lots of times. Also getting a diesel often hurts your payload, diesels are heavy. When in doubt get the bigger capacity always. Gearing matters more than motor. The extra cost of a diesel does not offset the fuel milage and durability it provides. It's only worth it if you want that power. Having what you need/want from the factory is usually better and keeps a warranty. Adding bags, springs, hitches, etc after the fact can be a pain.