Why would you go dualie then? I figured SRW with 6.7' bed would be better driving w/o the 5th attached, better to get in and out of parking lots etc...
AS one poster say the 3500 srw has a 7000 rawr = around 3500-3600 lb max load in the bed payloads.
The 3500 DRW has those big 9750 lb RAWR for approx 6000-6200 lbs in the bed payloads.
The trucks rear axle will carry all the trailer hitch load plus other necessary junk we throw in the truck so how much weight are you carrying.
The SRW/DRW have the same engine tranny so both will pull about the same weight.