Fire main can clear Exams easier. You'll be switching to Fire a lot at higher levels to do that.

Wind main is the god of Kyuubi, Fire main the god of Exams, Lightning main the god of Survival, Water main the god of Arena, Earth main the god of Strong Approaching and other instances.

So pick what you want to be good at... if you just want to be good at pvp, that purely depends on the meta. You can counter every team with the right team.