What are the gameplay differences between the nomadic factions?

[Tristuskhan]

... so playing Sarmatians you will most likely field armies of locals with very short lives backed by an uber-elite Roxolani Nobles or equivalent. It makes the battles trickier if you don't want your generals to get bad traits by retreating once the quivers are empty. you'll have to attack strong infantery with your peasants-in-arms and move your cavalry fast enough for your footmen not to be slaughtered. And even in victories your footmen will be slaughtered anyways. It's likely you'll rely on mercenaries and the ables one are a financial disaster for your economy. it's likely you begin to love those expensive hardened footmen and treat them with particular attention.

Playing Sarmatians roleplaying is compulsory: micro roleplaying. It's likely you'll know the name of everyone of those odd greek phalanxmen. Strange thing for a nomad.