I think the 3 stage generally lifts higher. Not sure how important that is though since they both lift high enough dump most anything you can put in there. A steep dump angle is kind of wasted on trailers anyways because the box isn't high off the ground like a dump truck. There isn't anywhere for the material to go once you start dumping so most dump trailers leave long piles rather than high piles. With all that said, I wouldn't pay more for a 3 stage over a scissor but if the cost was the same then I would probably go with the 3 stage.