Axle ratio is A LOT less important than it used to be with todays wide ratio 6 8 or 10 speed transmissions. Crawl ratio with a modern 6 speed and a 3.21 is better than the old 4spds with a 4.56. The gears are closer spaced making it easier to keep in the power band. Given a choice, the 3.92 is better and will be more enjoyable, but a 3.21 is not a deal killer like it used to be.
Payload is the biggest issues with half tons, especially Ram. A few years ago Ram changed their general design philosophy to aim more squarely at the demographics. The vast majority of 1500 buyers want a nice car with a big trunk to carry awkward items and maybe to tow the jet skies or the bass boat to the lake. Most people looking to tow a RV were looking at 2500. So they softened the ride and added amenities to the 1500 to aim for the biggest audience. The result is if looking at a Ram and planning to tow anything bigger than a speed boat, you should be looking at a 2500. That is what Ram intends, but unfortunately most salesmen don't know or understand this and just want you to sign on the line.