Both are gorgeous bags, but the Ali is considerably larger than the shoulder bag. It was simply too big for me. I think it just depends on how much you carry and how you like the bag to fall, as the strap on the Ali is longer, too. I think you just have to try them on to decide which is right for you and feels most comfortable for you.
I bought the Legacy Hippie as a compromise between the Ali and the shoulder bag, but now I am considering getting the shoulder bag, too!
I love the Ali bag! I think the Ali is a really good sized bag that would fit any body shape. I like having not to worry if my bag is big enough to carry what I need and the Ali is perfect for just throwing whatever you need in there and going.
I have the shoulder bag and I love it, but I'm also not a fan of huge bags. For me, the Ali is beautiful, but just too big. The shoulder bag is surprsingly roomy, especially with all the outside pockets!