Thanks goober, but looking at the photos alone it seems the cheaper one may cause a lot of friction on the side of the legs.
Notice the a.p. belt and how the resistance is from behind out of the way.
And then the lower costing device.
It also appears this one is made of rubber resistance bands while the ap belt is made of bungee cord type material. I'm not sure if any of it makes a difference. I just wanted to note the initial differences I saw in case anyone was trying to decide between the two.