NRA is much bigger at roughly 5 million members, but it has also been around and popular much longer than the GOA (2 million members). However you can bet a lot of those members are changing sides, as evidenced here. Also, it stands to note that many firearms manufacturers partner with the NRA and include NRA pamphlets in the boxes of all their new guns. GOA does not have that level of exposure yet.
NRA is much bigger at roughly 5 million members, but it has also been around and popular much longer than the GOA (2 million members). However you can bet a lot of those members are changing sides, as evidenced here. Also, it stands to note that many firearms manufacturers partner with the NRA and include NRA pamphlets in the boxes of all their new guns. GOA does not have that level of exposure yet.