I had a 2013 1500 5.7 Hemi (67,000 miles) and currently a 2018 2500 6.4 Hemi (22,000 miles). My son has a 2018 2500 6.4 with 78,000 miles. Step-son had a 2010 with about 30,000 miles, then a 2015 that he put about 25,000 on, then a 2019 that he put about 15,000 on. Step-father had a 2008, 2011, 2014, and currently a 2017 (all 1500's) and put about 50,000 on each of them and none have ever had any engine issues. My son has towed his 8000lb TT about 8000 miles with his 2500 and I towed my step-sons new 9300lb TT a few weeks ago and they tow fine. Can barely tell they are there.
Not sure what noise the poster above is referring to? No noise from any of mine. But those Cummins sound horrible and stink bad. lol. Ok, off topic there but you get my point.
But I agree with other posts. If you are towing over about 11,000-12,000lbs then go with a 3500 Cummins. With a 2500 you risk running out of payload. A typical 12,000lb TT will have about 1500-1800lbs tongue weight and will only have about 2100lbs of payload so with nobody in the truck you are already down to only about 300-500lbs of payload left. Less than 12,000lbs and I think the 6.4 will be fine unless you are towing in hilly terrain or towing often. The only way I would recommend a 2500 Cummins is if you are staying under about 8000-9000lb trailer and at that point unless you WANT the diesel I think the 6.4 is more than enough. If you think you may ever consider a 5th wheel then definitely avoid the 2500 Cummins and go straight to the 3500