After looking at the display models at the Verizon store, I chose to order an Arctic Silver S8+, though I did consider Midnight Black as well. Normally I like black on my phones. But like what some have said here, I did notice that Midnight Black tended to show much more fingerprints, which I felt detracted from the phone's aesthetic appeal. I didn't get a chance to look at an Orchid Gray model, but when I compared the Arctic Silver to Midnight Black, I felt that the Arctic Silver had a more premium look to the phone and didn't show as much (if any) fingerprints.
I never use a case for my phones as I take good care of them, so how the phone looks without a case is something I consider when buying one.