When I got my new phone near the end of last year I bought a gel case for it; while gel cases are smooth, glossy and nice to look at, they are sensitive to fingerprints and, worse yet, they becomes slippery if your hands are sweaty or otherwise slightly damp. I recently decided to get a tyre tread silicone case and I am satisfied with my new accessory: the silicone is not slippery when my hands are sweaty and the tyre tread-like engraving on the back further enhances the grip.
My previous phone had a silicone case; it wasn't tyre tread but it was a better case than the gel case was. I recently felt that silicone case again (it's Dad's phone now) and remembered how effective it was against sweat during last year's summer; as such, I had another look at silicone cases and I'm glad I did!
My brother also now has a silicone case and Dad is going to get one for his next phone, too; both of them have/want tyre tread types like mine. I had been considering a flip case but what I have is superior to them; I'm not keen on magnetic fields near my phone and most flip cases use a magnet to close.