Freedom,
The answer is so simple that it hardly bears a response, not to be blunt.
For legislative action (since you posted in this forum, I'll assume that's your interest) there's nothing better in town that the NRA's Institute for Legislative Action. For example, go ahead and search through the last National Review, and see who they thinks owns Congress. I'll give you a hint, it is not the GOA.
From what I can tell, GOA is single focused - legislation. NRA is considerably more diverse showing leadership and support through out the shooting community.
Then there's the size. The NRA is more than 10 times the size of the GOA. Who do you want working for you, an organization representing 3.5 million, or one less than 1/10 that size. That comes down to an argument that even a Congressman can understand.
So if you had $50 to invest in an advocacy group for our community, where would the money do the best work? Do the math, dude...
Thanks,