I prefer to go naked but I used to find that even seemingly empty pockets could end up scratching phones (I had a 4S that picked up two deep scratches in its screen while in an empty pocket, still no idea how that happened) so I switched to using a pouch style case that would keep my phone safe while I wasn't using it but still let me get the phone out easily and use it as it was.
That worked fine for my 4S and 5, but then my 6S arrived and I immediately found two snags - first that camera hump on the back means it's basically designed to have a case on it in order to lay straight, and secondly it's so damn slippery! They made the thing like a bar of soap, so literally on day one of having it I'd dropped the thing caseless three times and had scratches on all four corners as a result.
So now I've given up on the pouch and have got a wallet style case that covers it entirely (the screen cover flips out the way and latches with a magnet). I don't get to the see the phone at all, but I can grip it easily, it's not going to get dropped, and it will be ok even if it is.