I dislike cases due to the bulk, but with the glass front/back, this phone is slippery, so I knew I needed something. My biggest concerns was it fitting in my car holster (didn't want to purchase another one of those too) and adding too much bulk.
I initially purchased the Spigen Neo Hybrid Crystal but instantly disliked how bulky it was. The lip was really high, I had issues moving apps from one screen to another. Overall though, if I was looking for protection, nice case, looked great, seemed like good quality. Not easy to get on/off, but sometimes, that's what makes it great.
I ended up buying the Spigen Thin Fit. Can't say there's any protection with it, only that it's grippy so I won't drop it. But like I said, I was looking for minimal bulk. I like that the top/bottom doesn't have the lip (stuff won't collect under the lips and scratch the screen - have had that happen before). I also like that all the buttons and ports aren't recessed. But the biggest reason I like it, even with the case, it's still more narrow than my naked S5 and also thinner (I had the wireless case on the back).