Interested in the game

Hi,

I'm interested in the game and I've seen that there's a lot of expansions to root available. While I know that you can just play with base game but if I like the game enough I might get few later.

My question is, are fractions balanced against each other or newer ones are just better?

I know that strategy is important but from objective point of view is there a fraction that is clearly dominating the game?