I personally HATE cases for phones, they add bulk to it and ruin the whole look and feel of the phone. The #1 reason why I buy a phone is because of the design and a case covers it up. I know that you need to protect your phone but that's what a tempered glass screen protector and skins (Google them if you don't know what they are for).
My question is why do you use cases for such pretty devices like the IPhone 6s and Galaxy s7?
No. It's useless to get a bright color and then hide it with a phone case. I have a silver phone but I still like the color. Cases are annoying to deal with too.
Yes, because in my case the iPhone 6s is kinda slippery at times to hold. Like, even when I'm in the house, i have the case on. It gives the phone the grip it doesn't have naturally.
Anyway, the case i have is a rose gold like transparent case. I love it, it's simple and does the job.
With my current phone (iPhone 5) I used a case since the day I got it but I totally regret it.
Ruins the feel of the phone & marks all the back and edges.
I'd have taken it off but because it's scuffed the edges of my phone I have to keep it covered.
With my next phone i'm just gonna use some sparkly stickers to cover it all.
This is what I'm using right now, because it looks nice, shows off the color of the phone, maintains most of the beauty of the phone's design, and provides protection.