Though I prefer a metal frame to protect the screen from bending forces, I'm a big fan of plastic backs. My phone has just survived a metre drop onto concrete - the glass screen protector was destroyed but everything else is perfectly intact and I really think that a glass backed phone would have been landfill.
My one annoyance with 5G, however, is that the phones seem to be huge even when, as in this case, the mm bands are missing. I assume that this is because a lot of room is needed to fit all the antennae. The reason this isn't on my replacement list for my wife's phone is simply that she wouldn't have anywhere to put it.