What XJ... said... .
If your concerned about the weight limit you can put over the rear axle, you only gain about 900 lbs in the SRW 3500 over the 2500. If you have a fifth wheel with front slide outs, you will be close, if not over, for a lot of the current fifth wheels. Most of them have a pin weight of 2-3000 lbs (empty).
I looked at this about a year ago. I wanted to increase my load capabilities but didn't want the training wheel model. It just wasn't enough difference in load capabilities over my current 01 2500 to make the switch...