I had a 2500 and had to trade it in to get a new 3500 because I was overloaded with my 12k lb. 5th. My advice is to buy the 3500 for just a few dollars more. My wife and I have found that the new 3500 GMC is the best riding vehicle we have EVER owned, car or truck! It's really quite amazing, and it pulls my 5th like it isn't even there! What a difference between my 2008 2500 and my 2015 3500.
BTW - if you are thinking of the Ram, consider the fact that to get the torque ratings they claim, they use VERY low geared rear ends that affect mileage. I am agnostic when it comes to brands of trucks. i just want the best power train I can get. I think the Cummins engine is great but my GMC Duramax package with the Allison transmission is as good as it gets. The Allison was the final determining factor for me and I have been very happy with it.
Whatever your choose, bet of luck my friend!