The current crop of duallies will give you the ability to tow most any fifth wheel you may consider now or in the future. A 3500SRW series will limit you to around 14,500GVWR. Besides two more tires to purchase a dually will be a bit wider to park. And will be more stable towing. Neither are really suited for parking garages, or down town parking.
As for which one? Go drive them all,preferably all on the same day and over the same road. Then decide which one DW likes best and buy that one. Their all decent now days, and they all have quirks that you may or may not accept.