The one major thing about the S cases that make me keep it and not replace it is the sides.
They're grooved in a way that ensures you have a good grip all the time. It's spikey, or something like that BUT it feels perfectly smooth so you don't notice it.
Also you don't have to hold it firmly to get this non-slip effect. I was surprised at the design because they really did think about how people would use it and added this enhancement.