How much do you tow?
How much do you load into the bed?
Now those two questions are paramount for the necessity or usefulness of any opinions to your question. There are other lesser points of interest. If normal driving is a lot, the Cummins normally gives less fuel mileage. If money is an issue, that is important along with the probably increased cost of buying the 2500. Factor in the increase cost of registration, insurance, some parts (larger, beefier and more expensive), higher profile for garage and operation, parking, overall weight gain etc. Some just like the feeling of "manlyhood" they get from a bigger, higher more prominent vehicle. That's a positive to some who literally have no use for the bigger truck. You can more easily fit in with the horsey crowd and stand out in the bar parking lot. Get some stickers and vertical exhaust pipes when you are doing that.
I had both a Duramax and a Cummins. My Duramax was more Duro-junk. The Cummins was wonderful for near 200,000 miles then it started to cause me expensive trouble the next 40K plus. The modern Cummins has the same emissions crap as the Ecodiesel. Do a full delete and it really is designed to go 300K or more. Now if you keep it that long - miles and years - get the Cummins and do a full delete.
Sure the ride is a bit rougher than a little 1500. Sure you need some kind of steps, running boards or a ladder to get in and out. It is better to look down at stopped traffic next to you and see what you can see. Might be just what you want?