Whichever appeals more to you. Personally, I don't worry much about the back color, though I do prefer a white bezel. Not necessarily for aesthetic reasons, but for practical ones: I use mostly light-themed apps, browse a lot, write a lot. The white bezel is much easier on the eyes for me. If I mostly watched movies or worked in a dark room, or at night, I'd prefer a black bezel. So for me, the bezel choice is mostly a matter of how I use a device.
Anyway, my iPad Pro is gold with a white bezel. I would have been happy with the silver one also, but gold was available and so I went with that (my Air 2 is silver/white).
I Agree with your views on the differences with the iPad colors and bezels. I personally choose whatever iPad is widely available and colors only superficial to me, no matter if it's a black bezel or white bezel. I have used both colors over the years and you eventually adjust to what you have. It really comes down to the experience with the iPad over the color after so long. (Unless someone strictly prefers one color only.)