There is a little more to this on a car, being the factory shaft is a two piece the hanger bearing is surrounded by a soft rubber. when you step on the gas hard or let out the clutch fast the hanger moves up about .750 to 1.00 so the shaft has what we call hanger lag, with the single shaft the drivetrain is more direct or athletic feeling. the response is more direct and solid. I see another manufacturer mentioned in the thread. keep in mind all DSS shafts are balanced on a one of a kind cutom made balancer. These shafts are balanced to actual speed, most balancers do not spin this fast they are only looking for weight centerlines and sometimes miss what this machines see's.
take a look (not the best video but it gives you a good idea)