Depends on the type of Silicone. The floppy sticky type? Not a fan at all. The type used on the Apple silicon cases? (which is a soft-touch design that adds a little grip but not much). I really like it.
Not a huge fan of many hard plastic cases, though if designed right, I like them a lot. I used the Apple leather case on my 5S, along with an Incipio TPU case that I also liked a lot. For my 6 I have the Apple silicone case, which will likely be my primary for a while. I also have a Spigen Neo Hybrid which is OK, but will be more a change of pace case. I also just ordered an Elago Duro, which is rubber and plastic, for times I need more durability. Not sure if it's silicone or TPU.