For what it's worth: The rear axle and drive shaft in 2011+ gas GM 3500 is larger than 2011+ gas GM 2500. The axles are the same size with DMAX diesel 2500 and 3500. May not be true for Ford / Dodge.
I was exceeding payload with my fiver in my previous 2500 so upgraded to 3500 srw. I am now comfortably within all posted weight ratings with the 1 ton. I have a family to keep safe and don't need the liability if something were to happen with an over weighted truck. This is me, and to each his own.
By the way, the 1 ton handles significantly better under load than my 3/4 ton did. No more bottoming out.