I think the food at Bouchon, particularly the specials, is more interesting that at DB, and I prefer the wine list there as well. I also like the room more and particularly the outside seating in clement weather. I think the Wynn "lake" is kind of cool, but I thought the room seemed kind of cold. Also, I really like the raw bar at Bouchon; they always have a great selection of oysters.
That being said, last time we ate at Bouchon, I had the trout, and I wouldn't recommend it. There was nothing wrong with it, but we thought it was bland. My husband, on the other hand, had some brisket that had been cooked sous vide, and it was great. I also really like their soups.
We should try DB again, because we've only been twice, and relatively close to opening, but in the Wynn, we usually end up at Okada....