In turn I've owned a 1-ton International 4X4 pickup manual trans (15 yrs), a Chevy 1-ton 4-dr 4X2 DRW long-bed pickup auto trans & posi-trac (14 yrs), and since 2003 my '03 Dodge QC 3500 LB SRW 48RE & LS.
With the 4X4 I only used 4WD 3 times: Once to play in the snow; once front-wheel-drive only, to get home about 100 miles when the rear U-joints failed; and one summer to make extra money pulling tourists out of deep sand along the beach.
The DRW Chevy crew-cab 4X2 pulled well, but the fuel mileage was miserable, and for my purposes the dual-rear-wheels were merely an added expense, while the stability they offered was not often used. And, little noted: DRWs are hard to balance in synch; there's always some extra vibration. Twice I became stuck in soft ground (sand) in that vehicle, but a load of rocks on one occasion and load of small children on the second occasion got me going again.
To date I've towed an enclosed 2-axle cargo trailer a total of approx 8,100 miles with my 03 Dodge. This mileage was six 1,350-mile trips on the interstate, each lasting 2-1/2 days. My experiences on those 6 occasions were uneventful; the truck ran smoothly at a steady 65 MPH, and the trailer -- loaded to a total gross weight of around 8,000 lbs each time -- followed along smoothly with little effect on driving. Miles-per-gallon were affected more by air/wind resistance on the front of the trailer than by the weight; MPG readings were only about 1/4 mile-per-gallon (. 25 MPG) different between loaded (8,000 lbs) and unloaded (2,500 lbs). I did not notice any difference in stability between towing with the Chevy DRW and the Dodge SRW; and the Chevy with its 454 cu in gas engine was MUCH more affected by the weight of the tow than the Dodge diesel.
Over the years I decided that I didn't need 4WD, and that I didn't need DRWs. The fellow that mentioned all the extra running gear of a 4WD and its associated expense, including merely hauling the extra machinery around while not engaging it is correct, IMO. About five months after buying the Dodge I did become stuck in a snowy, smooth driveway in a rural area. 4 adults sitting on the open tailgate got me going again. In February of '05 I became imobile on an ice-glazed rural road while ascending a gentle hill; but the 4WDs were also having a great deal of trouble. After that experience I bought two Cooper mud-and-snow tires, mounted them on extra wheels and keep them covered up in the garage. So far, I haven't had to mount them. But this coming winter I'll be back in the colder, rural area and will install them for two or three months, along with about 1,000 lbs of concrete blocks in the bed.