The core difference between rhythm and repetition is that rhythm implies movement, progress, and sometimes surprising variations. Waltz is all about rhythm and includes a step, slide, and step in 3/4 time. On the contrary, marching is a repetition of monotonous footsteps without any irregularities.

That said, rhythm should always include some element of repetition. It creates a pattern that keeps users feeling grounded on the page. Compositions with entirely random elements don't create a sense of rhythm or repetition.^[1]