I have a somewhat biased opinion as I have has terrible luck with a Cummins. I had a 1999 24 Valve that lost 3 lift pumps, 2 injection pumps, and a cracked block. The only mods were a BHAF, 4" exhaust, and an edge (never pierced the wire). It was a great truck when it ran but no matter what anyone says the Cummins will eventually need repairs and those repairs are very pricey compared to a gas motor. Funny thing is thus auto trans in my cummins was still original and untouched At 175,000 miles. I sold the truck at 150,000 miles and bought it from the original owner at 120,000 over the 30,000 miles I owned it it was well over 10,000 in repairs. The Power Wagon gets my vote hands down. I have a set of Power Wagon axles under my current 99 Ram V-10 QCSB and they are hella stout. I personally would never buy a truck new but that is just me. If you decide to order one check out the expanded color availability on the ST models from Ram. You can get 4 different shades of yellow, a sublime green, even national fire safety yellow/green, John Deer green, Case red etc...
Two other things that may or may not be a factor for you:
Diesel availability near you, it is not bad for me, but not all stations especially in more urban areas don't carry diesel and many that do have old stale fuel with a lot of moisture just because they don't sell a lot. I have been driving for 30 years and the only 2 times I've had bad fuel have both been diesel.
The other is weather if the truck does not get driven a lot there is a good chance of getting gelling due to summer fuel still being in the tank when you get an early freeze late fall or early winter.
With gas being 70 to 90 cents a gallon cheaper, combined
with the extra maintenance costs of a diesel the gasser is an obvious choice.
You can always add a CAI, Cat back and tuner to the Hemi as well. They really respond well to bolt on mods. If that is still not enough you can add a supercharger