We like both. DH likes Biergarten more because of buffet style. Also, you can listen to the music. It's loud, more cafateria style tables, but certainly fun and good if you like German food (we do). Also, I don't worry so much if DS (age 2) isn't behaving well.
Chefs de France I also like a lot. It's definately a quieter place. I think price wise, it can run a bit more depending on how much you eat. It's my preference, but also the screaming child sticks out a bit more if he's having a bad day. Also, I've noticed that you can wait quite a bit after your PS time for a table - in December our wait was an additional 30 min.