What are the advantages and disadvantages of the Persian Empire?

Answer 1

It brought a degree of peace and consequent improved prosperity to western Asia and south eastern Africa.

However by taking control of the Greek city-states of Asia Minor, it involved itself in the Greek world, and its intervention in the cities within the Empire. Persia thought that it could overcome this by incorporating the cities of mainland Greece within the Empire under friendly local tyrants, and so establish an ethnic frontier on the west of the Empire. This worked with some cities, but many of the Greek cities resisted and the resultant wars went on for fifty years until Persia gave up and left the cities to go back to their usual fighting amongst each other.