When Apple first introduced the Product Red iPhone 7 line, I remember that the faceplate was white, and there was a huge outcry (at least here on iMore) that the face plate should have been black. I thought the white was ok, but, when Apple released the Product Red iPhone 8 line, with the black face, I could see what the hullabaloo had been about. I do think the black faceplate on the Product Red phones looks better.
As for the other colors, I think it depends. I loved my silver 6s with the white faceplate and my Gold 8 Plus with the white faceplate. So I guess in most cases I lean towards white, even though when I got my first iPhone (a 4) it was black, and I couldn't imagine having anything else. How times change!!!