You want to keep in mind that in any MMO, large population servers have downsides to them. One of the biggest downsides at the current time for high population servers is that they aren't the best servers to access features such as housing. So it would be recommended that you look at all the features of this game and decide a server properly based on which features your interested. Many people made the mistake of joining large servers to realize the feature they were anticipating the most such as housing was highly inaccessible.