A:
The difference between the s model and the C model is that the S model is slightly slimmer than the C model. Also, the S model is made with a metallic type of casing, whereas the C model is made of plastic-like type of casing. Notice that the S models, there isn't many color options associated with it. That's why Apply made the C model, "C" meaning "color". It offers users options to get their phone in a variety of different color casings.
I hope this answer was helpful to you.