I'd go for the diesel, the cost bump is around 8 to 10% of the price (of course dependent of the MSRP).
DEF issues were grossly overstated mostly due to dealers claiming "bad DEF" when the trucks would come in for emissions service. Then there was a lot of loose talk that spurred from the dealer's claims on various forums, all unfounded.
Chrysler issued two recalls on 2013 through 2015 2500 and 3500's equipped with the Cummins. The recalls replaced the SRC, eliminated an ammonia sensor, and added new ECM software. Since the recalls, the conversation about DEF and dealer claims of "bad DEF" have disappeared from the forums.
DEF isn't as delicate as some would lead you to believe. From Cummins;
https://www.cumminsfiltration.com/def
https://www.cumminsfiltration.com/south-pacific/adblue-diesel-exhaust-fluid
There is a lot of talk floating around on the Internet about DEF and diesel engines, most of it is completely wrong, no surprise there. I don't know how many times I've read a phrase that went some like "all that emissions crap", or the "emissions cause unreliability". This typically comes from someone that never owned a modern diesel. The fact is, the current emissions make the diesel more efficent, longer lasting, and air cleaning vehicle (in some cities that is). The diesel emissions have been moved from the engine downstream to the exhaust. The engine is now tuned for efficiency and not for emissions. This emission design has been in operation on over the road diesels since 2010 and now on our pick-ups.