I wouldn't characterize the Evutec as slippery. Actually, I rather like the rubbery coating it has, as it strikes a nice balance between offering some grip, but not too much so that it becomes an issue when extracting it from pockets, or collecting detritus like dry silicone cases do. I've never handled a Play Proof, but to me, something like a Speck Candyshell and its hard plastic can be slippery, especially when wet. But I have had two of the Grip versions for both 5 and 6, which I like for their grip (especially for $10 from a discount dept. store).
My comment was really about the kevlar veneer layer not providing any benefit in this application, except for looks. The protection comes from the TPU layer, but ultimately, a case is still a thin plastic shell that can only do so much.
As I've said before, my only beef with the Karbon is the price. It falls outside my price sensitivity boundaries when there are more interesting looking choices for that kind of money. When not up close, it looks like any other piece of black plastic. YMMV.
Their new Kaleidoscope and Texture lines are priced more sanely, and I like the looks of the former. If they're similar to the Karbon, they should be good options.
It can be hard, but you can't keep agonizing over the perfect case; nothing prevents you from changing your mind, or getting more than one.
