Hands down, the Biscayne Bay GM. It is a GREAT shoulder bag and fits so much. A close second would be the Houston though because it's roomy, it just isn't as comfy on the shoulder for most people. I wear it on mine but a lot of people find the wide bottom too cumbersome.
If the BB GM comes in Amarante I'll get that one but otherwise, it's a Reade PM since that's the one decent style in the Vernis bags that I don't have yet (I have the BB GM, Petronia St., Lexington, 2 Houstons and a Bedford).
My favorite is definitely the Houston. I saw a woman with a Pomme one the other day- just gorgeous, and it's the perfect size- not too big, not too small. I'm partial to shoulder bags myself, and it holds a lot. I think it will look beautiful in Amarante