You might want to consider leveraging the World Rebalancing Initiative which allowed free transfers from Congested Servers to Prefered servers.
Balmung and Gilgamesh are the congested servers in the Aether data center.

The most recent list of preferred servers I could find.
Jenova
Brynhildr
Famfrit
Malboro
Of these, I see people from Jenova the most in cross world duty finders. So, that might be a good indicator of a lower population with high activity.