I have never RPed on Balmung, but I enjoy it a lot. It's a very lively server and I've made a lot of awesome friends (across all skill levels) on it.

While I can't compare each server in depth... I think you'd be able to enjoy any of them. They all have their stereotypes, but that's never the only thing going on. There are plenty of groups clearing T13 on Balmung, for example.

The downside to very high pop servers... forget about being able to ever have a house. So far nothing else in XIV has a hard limit on how many people can participate, but if they add something else similarly limited, expect it to be in the same boat.

Whichever server you pick, have fun!