I was in a 2013 RAM 2500 CTD with the leaf spring rear suspension, and a 2014 RAM 2500 CTD with the coil springs back to back on Monday (2 days ago). My BIL was shopping. I rode in the passenger seat.
The ride stiffness is pretty close to the same, but the lack of "jitter" over small road imperfections was night and day different. Very noticeable. The suspension harshness was noticeable less on the 2014 truck. Over large bumps, the "stiffness" of the springs felt about the same.
Best idea is to go for a test drive. It's really a dramatic difference.
The payload on my truck should be somewhere just over 3000#. The payload listed on the website and in the brochure is 3250#.