Size is important
The reason they are so much faster is the surface area, with the orginal clay bars falling well short of the area of a clay towels surface, that is about 8 times larger (as you can see in the image with the yellow clay bar sitting on top of the Clay Towel).
Since we first got them, we have found them a lot faster and easier to use. As they are so fast, it's now a rare occasion we ever go back to using the clay bars anymore.