Ottoman's get free unit production with military schools as well as faster production in blacksmith influence. Also producing units and ageing up gives your expirence towards vizier points, which can unlock special bonis.

The Byzantines get the cistern system which increases gathering rate and can be toogled to eithe faster production or research speed. On top of that they get an additional resource, olive oil which they passivly produce from food gathering and can be used to purchase mercenary units from other factions.