The Muse and the Stam are two very different bags. I have both styles, and I love both styles. I get more use out of my Muses, and if I had to chose between the two styles, my vote would be for the Muse.
The Stam is whimsical and girly and kind of quirky. The kisslock and the gold chain are very nice throwbacks.
The Muse on the other hand is professional and classy and ladylike. There are three different sizes for you to chose from, and I think that each size says something different.
That being said, I am not a fan of the regular Ivory Stam. I've looked at it several times, and each time it has left me a little cold. For some reason the Ivory seems flat to me. I prefer the patent Chalk Stam over the regular leather one.
On the other hand, I think the Ivory Muse is absolutely stunning. The gold hardware is just the right color for the ivory leather. The bag is a head turner.
I don't think you can go wrong with either bag, and in the end I think it comes down to what you are looking to use the bag for. If you want a fun, not too serious bag, the Stam would be the best choice. But, if you want a bag that you can use in a professional setting, the Muse would be a better option. The Muse can be dressed down as well, and it looks fabulous with jeans, so you would be able to use it casually too. Good luck.