In reality, there are many who share characteristics of both. The principal characteristic of priests is that they are bureaucratic office holders. They are professionals who are entitled to perform rituals because of the position they hold in a religious organization. Such organizations are generally hierarchical. because they are bureaucrats, Priests are found only in State level societies. These are the only kinds of societies that have the necessary bureaucracies.
Priests derive their power through training and their position in the bureaucracy.
The principal characteristic of shamans is that they are independent operators who communicate directly with the real world of the supernatural. since they are independent, shamans are found in virtually every society, including our own. However, in band and tribal societies, they are generally the only type of cleric available. Priests and shamans can be compared on many different levels. In state level societies, priests and shamans form opposing poles of power. All material Richard L. Warms, 1997.