Always naked. I take AppleCare+ 'just in case'.
I've had every flagship iPhone model since the original and have never used a case, ever. I follow a few simple rules that let me do this and keep the phone pristine when it comes time to sell it/trade it in/etc the following year:
- I have a dedicated pocket for it (front left). Only two things ever go in that pocket: my iPhone, and my hand. Nothing else. Not even receipts.
- I don't set it down on hard surfaces.
- I don't let it go from a height (ie. drop it).
My experience has been a phone treated this way is often in better shape than a phone in a case. Most cases will collect bits of dust/grit in them, allowing micro-scratches to form on the phone itself.
If you don't treat your phone like a tv remote, it'll easily hold up and look the same as it did the day you got it.
My suspicion has always been that
because I don't use a case, I'm far less likely to drop it, bump it into things, etc, as there's a part of my brain that's very aware that I'm holding a high-precision, super sophisticated piece of marquis engineering in my hand which informs the way I handle it (eg. if I'm in a public area with a fair number of people around I hold my phone with a more secure grip, etc). Likewise, people that use cases can be more cavalier with how they treat their device, and hence are more likely to drop it, toss it on the counter, etc.
