The only other advantage of an open driveshaft I can think of, apart from those already mentioned, is that of a theoretical ride improvement. Studies of mechanics have shown that the greater the ration of sprung weight to unsprung weight, the smoother the ride.
For the torque tube drive system, essentially all of the differential /torque tube/driveshaft assembly is unsprung weight. For the open driveshaft, the driveshaft contributes little if any to unsprung weight. I suppose the trailing arms contribute a small amount.
meansam
