I had a Coussin PM and sold it - I had the original version where the outside zip contacted the inside up every time I zipped it, which I didn’t like. But the main reason I sold it was the poor war and tear I saw on used bags - maybe they were beat on, but I was worried about the debossed monogram fading over time as well as the bag looking deflated. Having said that, I think the newer model with leather lining and no colliding zipper is definitely an improvement over the version I had.
I have the Chanel 19 and it is one of my most used bags - it seems to be “relatively” hard wearing (there are pics in the Chanel pages of Tracy washing tomato sauce off the outside of her 19 in the sink with soap and it is fine! Not that I have personally tried this though

). I love the back pocket of the 19, and it holds a decent amount. I have an organizer from handbag angels with support for the bag sides and base to reduce structure loss over time, which I highly recommend if you like the rectangular shape. It really is an easy bag to throw on cross body (or hand carry) and go, and if you want to shoulder carry there are lots of ways on YouTube to shorten the strap with clips or wrapping it. Mine does not look sad and it is a couple of years old.
I have no personal experience with the YSL puffer, but I do like the look of it, and I like the option of short or long chain with the 4 grommets on the small and medium. It looks like the folded corners typically show some wear when you look at the used market, but the rest of the bag seems to hold up well!