We ran a 700 bushel Unverferth, with the hydralic drive, and it took more than double time to unload. Used it with a 8970 Deere, so had lots of hydralics....but its slow, and you have to be careful in tough grain, or she can stop on you.
We have cart mounted on a Big A run by hydraulics and it is slower to unload than a pto drive cart. But the guys more than make up for it with the speed between the combine and truck.