I have the black HTC One, and I would never consider covering it with a case. It's such a beautiful piece of hardware, why would you want to cover it with a hideously ugly case? If you don't care about aesthetics, you could buy a cheaper/uglier phone.
I have never understood the concept of using cases with phones, what's the purpose, to keep it scuff free & scratch free until when? 2 years down the track it will have ZERO resale value anyway. So that means for 2-3 years you have an ugly looking bulky phone, only to end up with a scratch free, phone, that just happens to be 100% useless at the end of it (outdated, outspecced, and worth nothing). It's like covering furniture with plastic - what's the point?