Medium, actually.

Since this game isn't PvP based, there isn't really an advantage to a high-pop server. In fact, I think it just creates more competition.

Low pop servers do make it hard to find others to interact with, however. No one wants to play in a ghost town.

I picked Besaid because it's the unofficial NA RP server, and I knew there would be a good, mature, English speaking community to interact with. I felt that would be the best home for my LS, and assure its longevity.