Here's the picture I tried posting earlier. You can see it has a shock to help absorb bumps. I like the exposed bag and shock because you can see it working and it's easier to adjust air pressure to set ride height.
Both units listed so far have a scissor action and both will allow the trailer to move up and down. The extra holes in the mount are for added adjustability to set bed rail clearence. Bed rail to coach clearence has never been an issue. I think with the reversed scissor action it has more control when braking as compared to the Reese. Also the Reese doesn't appear to have nearly as much travel making it more vulnerable to bottoming out.