I bought both the PM and the BB and ended up choosing the BB. I don’t really carry a lot on a daily basis, so the BB made most sense to get first. I am still considering the PM for later. The PM is only slightly bigger than the Palm Springs PM. A good size for everyday, but I think you might actually find it on the smaller size for travelling. It’s actually not that much bigger than the bb.
I have the Palm Springs PM and had the mini and I love the look of the Montsouris much more. Capacity-wise, mini PS and the bb hold the same. Functionality wise, the bucket style of the Montsouris is much better because everything is easily accessible. The mini has a front flap that only opens halfway down the bag (zipper doesn’t extend to the base). The rounded top of the mini means you have to reach through the front. So you can really only reach the front items easy. It’s a small bag making it a tight fit so trying to stick your hand in to pull something out can be challenging! It wasn’t uncommon for me to have to pull stuff in the front out first to get access items in the back our bottom. The mini’s front pocket is useless too so don’t count that as a bonus feature. The infamous lip over the zipper is the worst design flaw, but LV redesigned the bag late 2019, so if you buy one make sure to get the new one. The old design is impossible to open with one hand and the canvas cracks. My PM started showing cracking within 4 months of me owning it and I was very careful opening it!
I sold my mini PS for my bb. It just launched so only time will tell if it is as popular as the PS. Ultimately it comes down to personal taste. I think the PS is cute in a sporty, youthful way. The bb reminds me of the noe, still cute but in more of a classic, refined way. You can wear both bags multiple ways, but I find the mini always only looks like a backpack. the Montsouris looks like it could have been meant as a shoulder, crossbody, or backpack. I love the look of the Montsouris and the functionality is huge bonus.
