As I said, some people have found the metallic finish to be delicate, but not everyone has. I think it's important for people to know that. One person's bad experience doesn't mean all bags in that line are flawed. If someone owns a beaded bag and some beads fall off on one person's bag, if doesn't mean that this will happen to everyone who owns that bag. Sure, you have to take care with special finish bags (like beaded or metallic finish ones), which you should do with any leather in my view, but as long are you're aware of the risks associated with a leather type you could own the bag for a lifetime and not have a problem! Crocodile skin, swift leather and lambskin are all very 'delicate' leathers too!
I've owned my Diorama for just as long as the member on here who had the issue with wear on her corners, but my bag still looks 100% brand new, and I use mine all the time. Everyone will have a different experience.
Some of the metallic colours like blue or pink, in my opinion, show wear faster, because the metallic coating is a bright colour and the leather underneath appears to be a dark grey. With my silver diorama, because the coating is silver and the leather underneath is grey, you wouldn't be able to notice corner wear much anyway (especially with the perforated design). The gold might be slightly different, but I don't own it so I can't speak for that colour.
All bags and leather types have their pros and cons. Lambskin bags are just as if not more delicate than metallic and other special finish bags. The corner wear I've seen on some relatively new Chanel and Dior lambskin bags is horrendous. I'm quite scared of lambskin bags for this reason and don't own any of my own (yet), but lambskin bags are adored by most people here on TPF. I'm sure there are thousands of people who have never had an issue with their lambskin leather. It just depends on how you wear and care for your bag

Everyone will always have a different opinion, so you can only make the call for yourself.
I'm in no way trying to sell or convince anyone to buy the metallic Diorama, but people should be aware there are 2 sides to every story