Finally played a gb at mgc. We have a hobbit on route so I've gotten some good time on it. My answer is apples and oranges. They are two completely different beasts. They play different, feel different and are priced different. To be completely fair I think both are exceptional games. The bar has been raised and we are spoiled to get such great games right next to each other.
If you like the old mode based Williams style games. The Hobbits for you. Obviously stern has its own style as of the last handful of years and the GB follows suit and is a major step up for stern.
If I had to pick one.... Well luckily I don't have to. I ordered GB today. They will live side by side in harmony.