Gradient Flow moves a smooth spectrum through the letterforms continuously. The word itself stays still — the colour is what animates, cycling through the type without ever cutting.
A SMIL animation drives the gradient's stops along the fill rather than transforming the text, which is why the word never moves. gf-in handles the initial appearance and then hands off to the colour cycle.
Better than most styles here. Nothing translates or rotates, so a long line stays readable throughout — most animated styles get harder to read as the word gets longer.