Alas, all rear racks are not the same. Some are better used for just mounting a trunk rack bag to, others are better suited for panniers (but have too narrow of a platform to mount a trunk bag), some will do either/or but not both at the same time, and some will take panniers and trunks at the same time.

Don't know what you are wanting to haul, but based upon what you linked to, I'd go with the Topeak rack over that other one.