Wheel Surface: More than likely you're going to want smooth wheels, but there are some that prefer a wheel with a little bit of texture to it. (geekwrapped.com)
The volume rocker and power button are easy to locate and press, and the power button has a nice texture to it so you can tell which button is which. (digitaltrends.com)
I love that it is a neutral, but has great texture to it as well. (ladyinviolet.com)