I have a 9 pro and it was very slippery at first. I put it face down on a slanted table and it slid right off once.
Anyway, I took the case off after a while. It's not new anymore. Your mileage may vary, but despite dropping it a bunch, it hasn't shattered and the edge only shows some slight marks from falling.
I ride a motorcycle (not a big one), and it will slip out of my short's pocket onto the road pavement, every, single, time, without a case.
Motorcycle meant I went with quadlock case.
But am now in the quadlock system of attaching my phone to anything else.... IE car mounts too. SO quadlock got a bunch of my money.
Maybe I'm a buyer trying to justify my sunk costs, but to Quadlock's credit, once all matched, I think it works well.
And for the 3D printerists, there is a bunch of Quadlock 3D models to help out too.