After years of only using the saddle brown leather cases, I got a silicone case last year for use during the summer (sweat and sunscreen). For a while I would switch between the two, but I eventually decided that I prefer the silicone, so the aged but loved leather case stays in it’s original box.
I’m still using (and loving) my iPhone X so the only “Apple” silicone cases available to fit the X perfectly are the counterfeit ones. I’ve worn out a flash one, a black one, and am now on white. My next iPhone will be purchased with a white Apple silicone case because it’s my favorite so far.
EDIT: Leather is more luxurious in the hand and easier to slip in and out of a tight front pocket. It's also more likely to fall out of a loose gym shorts pocket when sitting down.
For various reasons, my phone is rarely in my pockets as much as before, so I now prefer silicone over leather because it's easier to lift from a table and sounds better being set back down, especially on glass. At home a lot more and being casual and tossing the phone around the bed more than usual, silicone grips where leather slips.
