I've been a Betsey customer for several years and I definitely prefer the Miracle Mile location over the Fashion Show. The store itself is much larger and better laid out.
Betsey's designs are unique and the salespeople are always fun and helpful. This is a great store to look for clothing for any occasion. There are pieces in this store that you won't see anywhere else.
The cons are the high prices (though there are 70% sales every so often), the lack of mirrors in the fitting rooms, and lately the product quality isn't what it used to be. The button work on many of my garments is subpar, and I recently had a button pop off of a cardigan within the first hour of wear.