Always case-less. It's a phone for God's sake, it's not a newborn child...you don't have to mother it. How about you wrap it in cotton wool to go with your screen protector? Some cling film might nicely protect the back too. Ugh, no. Cases rarely look good.
The way I see it, you're spending a lot of money on a 'designer' phone and then you're covering it up with a case that probably cost you £40 at the most and looks like rubbish, or which makes your phone about twice the thickness - bye bye all that hard work Apple put into providing you with a gorgeous, meticulously designed phone. Resell value isn't really an argument for me seeing as I sell my old iPhones to recycling centres who don't care about the natural cosmetic wear a phone is inevitably going to pick up. Never smashed an iPhone. Sure, it's scratched up and there's some pretty deep scratches on the back, but that's not typical. That's because I absolutely do not baby my iPhone. If all you spend your time doing is worrying about the price of your iPhone when you come to sell it, why are you buying one in the first place? You'd save ~100% of the costs by JUST NOT BUYING ONE.
Rant over.
Do what you like with your iPhone, it's yours.
Just don't be so silly.
Cause I'll just you.
Consider yourself judged.
<3
Ps. This post was mostly satirical but does loosely represent my views on iPhone cases. Please do not go out of your way to be personally offended by the content above.