If we specifically look at SLS (sodium lauryl sulphate) versus SCS (sodium coco sulphate); both ingredients are made in the same way, by treating fatty acids with sulphuric acid and then neutralising with an alkali. The difference between them is that SLS is made using purified and isolated Lauric acid, whereas SCS is made using whole Coconut oil.
The result of using these different starting materials is that SLS is a relatively simple molecule and has a small molecular mass enabling it to easily penetrate the outer layers of the skin and cause irritation to underlying living skin cells. On the other hand SCS has a more complex molecular structure which has a much greater molecular mass. This prevents it from penetrating the epidermis, and means that it has far less irritancy as it cannot reach the living cells under the skin surface.