I would say the Averni, simply because their generals have impeccable taste in terms of their battle wardrobe. I mean, who can withstand anyone who wears a giant swan helmet and dons the imperial purple?

On a perhaps related note, have been playing an Averni game, and on one turn my adviser popped up with a message from the Epirotes. They apparently wanted me to take a couple of Illyrian cities in exchange for vague promises of friendship, and I was suddenly allied to them when I accepted the offer by pressing on the advisers face. Is this some sorta timed mission or something? Might be another reason to go (or not go) Averni.