Looking at the Pill, the physical description is a golf ball with its sides shaved off. The Pill has the same weight and feels like a full golf ball. Contact produces the same sound. The lack of sides makes the Pill unstable when not struck correctly and that is what it is designed to help with.
The Momentus Swing Iron Trainer is a heavy weighted club with the same length and loft as a standard 7 iron. The molded grip helps to correct my grip into the proper position. If I find my swing feel begin to slip away, I grab my Momentus and get my hands back into position.