I'm going to go exactly in this order:
Wait until the game does release, and then wait a month. Why? Because Every-freaking-time the server gets mega stacked. There's 50 people trying to kill the same 10 [insert monster name here] as you, and this just makes it tedious, it also lets some players experiment with which class they actually want to be.
And then roll for the 'underdog' faction. I do not care which one of them it is, I will roll for the underdog.
There's some good reasoning after this. Mainly, usually the faction with a overwhelmingly larger amount of players is the "Immature faction". As in, has the biggest concentration of young players. I am not saying that young players are bad, I'm just expressing it tends to have more immature players. And those are the players you are going to have to deal with. Of COURSE there will be mature players, but my focus MMO-wise is specifically PVP. In PVP, most of the time you are teamed up with strangers, and it so happens that mature people stick to strategies that work a lot more.
And I don't really know where I'm going with this; I'm just saying that I am sure I'm not the only one thinking this way, so probably the game will balance itself pretty well.