I was in the same situation 9 years ago at a regional brewery. We used GW for our base malt but Briess for all the specialty. I beleive this was when GW first started doing there own specialties. Bottom line we tried GW and there was a definate flavor difference so we stayed with Briess. Really you need to do test batches to determine this. Your beers are unique and no one is going to be able to give you a definitive answer. You have to do side by sides and go from there.