@Tomma I have no information about people choosing faction based on visuals (althought I dont say that it cant exist at all, it can, and in medium and high rated also). I chose the faction I thought was best when I started. And all new players with who I have spoken, it was kind of the same. It is quite common questions like: "Is this faction the best?", "What is best faction?", "What faction should I play?", "Is x faction stronger than y?" etc. Those are common discussions with lower rated players. Also, every time I said in the lobby to low rated player, that his faction is hard to play/ weak/ bad for the spot, they always changed the faction.
I agree with you, that there is correlation between faction strenght and its popularity, and people choosing based on popularity, makes statistics only stronger.