Not all Greek city states were democratic. Many of them were oligarchies or monarchies while Athens had a temporary democracy.
You can also talk about how the Persians depended mostly on overland trade(Royal Road and later Silk Road) while the Greeks depended on maritime trade in the Mediterranean.
In addition, you can talk about slavery. Slavery was common in Greece, especially in Sparta while the Persians tended to look down on slavery because it was not seen in a positive light in Zoroastrianism.