I do not know anything about BGG other than what they share on their website -- which is that they sell clubs and sell dvd's that I guess will explain or tell you about their method. The "Method" tab on their site did not work.
I do know Graves and have been a student for five years (as of this August). I had been a NG golfer for four years before stumbling on Graves.
Graves uses Moe as a model and teaches his swing. I love that I can see video of Moe and try to imitate his positions. I know what I am trying to do. My index has dropped from 12.5 to 7.4 since finding Graves.
from 18.0 to 13.2 with NG
from 13.2 to 8.3 with GGA