I originally bought the Caseology Parallax. It fit nicely and was good for gripping, but the problem was I use a magnetic mount for my car which requires I put a metal plate inside the case. Since the whole case is flexible, the metal plate would slide around too much (I never use the adhesive to attach it to my phone or case).
So then I bought the Spigen Tough Armor case, which is a flexible inner layer and a hard shell outer layer. When I put the metal plate in against the phone, the magnetic pull was not very strong and my phone would kind of slide down a bit. So I tried putting the metal plate in between the hard shell and flexible inner layer and it works great! This has the added benefit of extra protection against the chance of the edge of the metal plate scratching the phone itself. As for the case itself, it's nice and looks great. The edges are fairly "sharp"...not really rounded at all...but it doesn't really bother me. The hard shell is pretty smooth and a fraction more 'slippery' than the Parallax, but also not something that bothers me. I think the only part I'm wary of is how flimsy the kickstand seems. I don't use it much, though.