Population-wise, Balmung is actually not as large as some of the other servers out there. I have characters on both Gilgamesh and Balmung and I can say that the population on Gil is most definitely larger than the one on Balmung.

The problem on Balmung (that no one seems to want to talk about or address) is the fact that many, many people will go AFK for hours on end and remain logged in, thus taking up a login space on the server. I'm quite sure that Balmung would become much more accessible if they just reimplemented the AFK auto-kick feature.