Each of these gyms trains very differently. In some gyms, all of the gymnasts train for elite. In others, there is a dual track and/or you may not have the elite coaches unless you are already an elite. Some gyms emphasize Top while others do not. You would not want to attend a gym that focused on Top if you were not built for that form of competition. Some gyms are better at bars while others are better at tumble/vault. Some gyms go to camp all of the time; others do not. Some gyms do hopes; others do not. Machine gyms tend to teach the same skills and progressions to everyone while smaller elite gyms do not. Some gyms are known for home-grown elites, while others are not. Some elite gyms train in large groups and/or with 10s, while others give virtually private lessons to their best athletes. Some coaches travel constantly with top athletes or for USAG reasons, while others do not.
In other words, the "best" elite gym for a promising athlete is not the best gym for a different promising athlete. It's important to be honest about the young athlete to find the right fit for her.