I have montsouris in turtledove, and it can be turned into a shoulder and crossbody bag. You do need a bandeau (around a full size LV bandeau length) to make it crossbody. I'm not really a backpack person, but montsouris felt like a good change of pace.
I really want to pick up pochette metis in the Since 1854 print/fabric. I never liked pochette metis until I saw it in that material. I don't want smaller crossbody bags anymore. For some reason though, I'm willing to make an exception for pochette metis lol
Between the two bags, montsouris carries a lot more, but it is a pit. I don't use shapers, and I organize all my things in pouches. I prefer pit-like bags because they suit how I organize.
Compartmentalized bags, like pochette metis, can be harder for me to use. I have to fit my pouches into pre-designated slots/sections. I think bags like pochette metis are more suited for people who throw their items into bags without the use of pouches, or other organization methods.
If pochette metis works perfectly for you, there's no harm in sticking to it. I have five neonoes in different materials and prints, and I'm looking to get another today... If you know something works for you and you enjoy it, there's no shame in getting that style again. If you do want something different, then get montsouris. Besides, you can always take it home, play with it, and see if it's something you would realistically use.
If I'm unsure about a purchase, I take it home and see if I want to use it before the return policy ends. If I don't, then it goes back. I'm someone that sees no value in owning something I won't use, no matter how much I like the look of it.