@Seirei Ship 1 was the first ship to open during the Beta for Xbox, and had a lot of players. But the servers were not prepared for the influx of people so for a while people were making characters on the other two ships as they they opened up. Eventually the JP players migrating to the NA decided to stay on Ship 2 in the west as well, so Ship 2 is where most of the veteran players seem to be/will be. Ship 3 seems to be comprised of people avoiding both Beta players (since nothing was wiped) and JP players, but it also seems to be the least populated. Ship 1 I believe has the most players though (I've seen Blocks 1, 2, and 3 get full, but whenever I check my character on Ship 2 I usually just see Block 1 full, but take that with a grain of salt because it could just be bad timing on my part).
Since none of the servers are full and Ship 1 is the first thing people will see when selecting a server, logically that is where most people will probably gravitate at first.
I am interested to see how this all changes when all 6 servers are open and server transfers are a thing. Ship 2 will probably always be the "JP" server though.
....And Balmung is a scary place >.<