I have the C's and the SL's.

It's not just the material, the SL's are definitely smoother and sleeker.

Suggest you try to find a place where you can hold both in your hands and spin them. Impossible to say whether they SL's are worth it for you because forty bucks is more or less precious in different amounts to different people.

Oh, FYI, the black rubs off pretty fast wherever your shoe comes in contact with it.

(get the SL's)