First lets look at the diagrams of both outfits...
and I think this really tells the tale of the two dueling outfits. Besides the fact that the Simplicity pattern is a "wardrobe" pattern and the Butterick one is just a dress/jacket combo, the draft of both the jacket and dress differ from pattern to pattern.
If you need a lot of fitting opportunities and a bustline seam that is lower, the Butterick pattern is the way to go. The princess seams in both the back and front of the dress will make this an easier fit and it is also drafted up to a size 24.
If you are looking for a Michelle Obama wardrobe then the Simplicity pattern would be your choice. There are pieces included that are typical of her working wardrobe and the draft on both the jacket and dress have less seams. Darts are used for fit in the dress along with a more flared skirt and the jacket back has a yoke and a center back seam.
Now Karen and I have both seen the original and we disagree on which looks more like the designer version. She thinks the Butterick...I think the Simplicity (which I already own in honor of full disclosure!). See this is the wonderful thing about sewing...if we so choose we can both purchase our respective choices and come up with our own versions of this infamous outfit.
So what do you think? Butterick or Simplicity pattern - which to you looks more like the First Lady's Inaugration Outfit? Inquiring minds want to know!?!