When I bought my iPhone 6 I also bought the brown leather apple case. It fits well and protects the back and sides well but I kinda think it looks ugly. I am now using a Moshi iglaze XT transparent case. You really have to look close to see that I actually have a case on the phone other wise it looks naked. So far I like this a lot better then the apple leather.
I'll be getting another case, this time the leather one in black. I really like the silicone one, but like I have stated in many other threads, it attracts lint and dust fairly easy. I kind of wish I went with leather to begin with
Going thin I got one of those cheap TPU cases on eBay. It's clear and adds nice grip and scratch protection but minimal drop protection. But for five dollars cannot be beat.
After using the Apple silicone case for a couple days now, this thing is a friggin lint magnet. Should've gotten the leather version. Guess I need to do that soon. Lol
I'm using a Spigen Tough Armor case for my 6 Plus, and I love it. Nothing to complain about. I'm sure you'd get the same satisfaction for the regular 6 variant.