We have not eaten at California Grill in years, so I can't be much help on that one. However, we have eaten at Concourse 2x in the last 3 trips. The food is always very good. We have not been rushed along like they do at some of the other restaurants. DD7 always enjoys their desserts. One time it was a cookie served on an artist's palette with the icing as "paints" complete with a paintbrush to decorate.
There is also quite a $$ difference between the 2 restaurants. CG I believe is 2 table service credits if you're on the dining plan, while Concourse is only 1.
I'm sure others will have some good advice!