Sharing my two cents...
As someone who owned the Stam and now owns the Ramona, I would say go for the Ramona. I actually traded in my Stam for the Ramona earlier in the fall. As a huge MJ fan, I was really disappointed with the Stam. The first one I owned had a defect (the colors of the handle faded within two weeks!). I ultimately decided that it was not the bag for me, especially as an everyday bag. The Stam is heavy and does not fit over the shoulder (not sure about the Spring 07 batch). I was also worried about the kisslock in general. The Ramona fits more perfectly with my everyday lifestyle.
Either way, they are gorgeous bags. I think you should consider which you'd get more use out of. Good luck!!