That's a tough call. Both are among our Top 5.
If you are looking for a quieter, more adult atmosphere, I'd pick BlueZoo. The ambiance & food are amazing. I have not seen many, if any, kids there. It is fairly quiet by WDW restaurant standards.
If you want fireworks & a view our over WDW and are able to enjoy yourselves even in the midst of alot of noise - CG is also good. But, I have to warn you, every single time we've been there, we have an over-extended child close by. DH & I can tune it out, but it's not always easy.