Both images capture motion.
Eadweard Muybridge:
Motion is shown with reference points, which is the previous frame.
The purpose is to show motion. Edweard Muybridge was a pioneer in the field of motion pictures.
Marcel Duchamp:
Motion is showed with time lapse. Each image of him is after the one before it. It also uses a reference point, which is the stairs.
I believe the purpose of the second photo is to relate to Marcel Duchamp's studies in kinetic art and studies of movement.
