I know everyone will have an opinion, but maybe consider the following with regard to the rear air. My experience with it is that, other than being automatic, it's just a very complex (and expensive) way to have the ability to change your "spring rate" as you change loads. It works reasonably well, but you have very little control over it in terms of adjusting on the fly. Basically you set the truck to "normal" or "alternate ride height" (those are the two driving modes). In alternate ride height the truck self levels and should hold itself there as you add the load. IT sometimes gets confused if you add a load and the truck is not running (you shut down while lowering on the trailer or camper), and then won't figure out where it is for a while. No great harm, just a warning light, but it's not perfect. The rear air in the 2500 is NOT like that in the 3500. It's your entire rear suspension (or it's your entire rear "spring".
I have the feature on my truck and, pulling a heavy 5th wheel, if I had it to do again, I'd just buy the coil spring truck and add airbags myself as I did on my prior truck. If you add an on-board compressor and in-cab controls you have lots of adjustability that you can control. I loved that setup. The one real advantage I've found with the rear-air system is, believe it or not, the ability to let the air OUT of the bags in the bag to load a motorcycle in the trailer. The truck drops a few inches which makes getting a motorcycle up a ramp and into a 4wd Ram truck a bit easier.
It has also been my experience that finding aftermarket suspension parts for the airbag trucks is tough. If you want a new sway bar to go with your heavy camper, or a lift (unlikely I suppose), or different shocks or whatever, you'll find many of the parts say "coil spring trucks only". Thuren Suspension now has some of it figured out, but the solutions are not perfect.
Just for consideration. I'm certainly not unhappy with mine, I just would do something different if I knew then what I know now.
By the way, the factory exhaust brake is terrific, and well worth the automatic transmission. I have a brand new Ford truck at work and the exhaust brake isn't nearly as good or as adjustable. The automatic transmission are very good now, with lots of manual control (to/haul and manual shifting) and torque converters that lock in nearly all of the forward gears so that the engine has a huge number of ratios to choose from. With that, you can easily haul a 3,000 camper and still run the 3.42 rear end. I tow an 11,000lb 5th wheel with mine (68RFE and 3.42 gears). and I can still get 21mpg on the highway empty if I keep the speeds down, or cruise at 80 at a low RPM.
Greg