I have both the Ali and the shoulder bag, both in leather. I love them both so much and they're equally wonderful in their own ways.
If you want something to go over a winter coat, Ali is definitely for you. It holds more than the shoulder bag, yet doesn't feel bukly in the least. It's pretty easy to get in and out of and it looks great on pretty much every body type.
I love my shoulder bag too, but if i had both of them in the same colour, the Ali would definitely win out. I love the two front pockets on the shoulder bag, but it doesn't fit against the body quite as well when it's full and although it does hold a lot for a bag it's size, it doesn't hold nearly as much as the Ali. There's no way i could fit gloves and a winter hat in it in addition to my other things. However, the ali would hold all that with room to spare.