Do you mean the NPC vs the Mamiya one? That is primarily a difference in brands. I have never used the NPC back, but I am certain it has a dark slide or you would have to shoot a whole pack of film to prevent losing a frame or more when you removed the back. The photo is showing the back side of the back and the dark slide is hidden around the right edge of the back in the photo. I just looked at the Mamiya N back and that is the same thing as the NPC, the dark slide is to the right and blocked by the angle of the photo. The thing you are seeing on the back of the others that looks like a film memo holder or something is a guide so that you can see what the frame will be like on your photo.
They all should work perfectly with your camera, I suspect that the one at the bottom that sells for a couple of bucks less is the older model that came out with the Super, but I am not sure about that.
Also, don't forget the Dead Link Removed if you are going to use it on a tripod. The back extends below the bottom of the camera and will interfere with mounting the camera on a tripod.
Paul.