Answer:
Western church was totally centralized and the Eastern wasn't.
Iconography of two churches is totally different.
Explanation:
Western church (Catholic) is under the authority of the Pope, who makes all important decisions. Hierarchy is showing his supreme influence in the centralized institution. In the Eastern (Orthodox) church organization is different, as there is a couple of patriarchs, who are bringing the main decisions. Among them, the most influential ones were from Constantinople, Antioch, Jerusalem, Alexandria...
In the Eastern church saints are usually presented on the frescos, while in the Western we usually have mosaics.
