Something not touched upon yet is stability of SRW vs DRW's while towing.
From my experience towing larger fivers with everything from 2500's to custom built International tractors; the steering corrections required when that tall slab-sided trailer is hit with either a cross wind or the pressure wave of a passing semi are going to be more frequent with a single axle and it's two tire - four sidewalls resisting side flex deflection than will be required for the dual axle, eight sidewalls.
Pick-ups, in an effort to give you towing capacity and comfortable ride, maintain the tall profile tire to offset harsher ride characteristics from stronger/stiffer spring rates. Those taller sidewalls are less able to resist flexing from side forces induced on them by the front of a tall trailer trying to push the rear of the truck sideways when hit by a crosswind. This results in you having to make frequent steering corrections as the rear of the truck is taken off it's straight forward line of travel.
I'd opt for the reduced requirement of steering inputs, extra margin of safety given by eight of those sidewalls resisting flex or tread lift along with two addtional contact patches for braking purposes over the single rear wheel and it's questionable width convenience advantage. JMHO.
