We've done both but it's been a few years. When we did go, we loved the GG, Chip and Dale were awesomne and the food was very good. Askerhaus we didn't like that much, although the princess interaction was good, we all thought the food was just OK and the whole thing was way overpriced. We love the breakfast at Chef Mickey and Crystal Palace, and this just seemed like a so much less appealing selection. For over $100 (for my family of 5) I didn't think it was worth it.
If you already have a princess meal and your son love C&D go for GG. Just my opinion, I know that others rave about Askerhaus.