What is a similarity between the Abbasid and Umayyad islamic empires?

The Umayyad dynasty undertook its administration work from Damascus while Abbasid did so from Baghdad. The fact that both caliphates managed their administration duties from their capital cities creates a common similarity between them two. Both Umayyad and Abbasid caliphates were made up of Sunni affiliated Muslims

Explanation:

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).