I think you misunderstood Dr. Jack's earlier comment about not having to cut a circle. If I understand correctly, the Millhouse TT comes as a circular piece of aluminum with some connected aluminum feet. You have to cut a circle in your layout and push the aluminum circle up from the bottom so that the feet can be screwed to your benchwork.
On the other hand, the Ross TT comes already attached to a hunk of square plywood. Thus, instead of cutting out a circle, with the Ross you just cut out a square. Many people find a square cut less daunting than a circular cut.