There are multiple opinions on how the realms will be balanced. Some people have said that Albion will be the least populated because of not having a good source of endurance regen. Paladins DO have an endu chant, but they're going to be locked down by CC most of the time since they don't have access to Determination (reduces time on mez, root, snare, stun, etc). They predict this will lead paladins to not getting very many groups.
According to a poll that I did, based upon U.S. players ONLY, Albion will have the highest NA population.
http://www.uthgard.net/forum/viewtop...351866#p351866
Hibernia won't have any issues with population because they have some powerful RA's, such as Group Purge from druids (removes all debuffs, mez etc).
Midgard should be well populated as well because they will have an advantage, at least early on while everyone is lower RR, due to them being the strongest melee realm.
My personal advise is to play whichever realm you like the most, and stick with your friends. This means, come with us p99'ers to Hibernia
[You must be logged in to view images. Log in or Register.] I don't really feel that there will be too much realm imbalance, but I do think that Albion will overall be the least populated, not to the point of it being a hindrance though.