to me, at the beginning time, it is with cover, and then later, I often take the cases off because the cases avoid the heat dissipation. For your consideration, I suggest you may choose some slim and transparent case which can protect from scratch and also show the beauty.
I use a case. I like them not only for protection, but I love being able to change the look of my phone. I have several cases, but since I got the white silicone case, I haven't switched cases. It's been a few weeks. Most days I take my case off once I'm home, but when I'm out my phone goes in a case.