As I observed the routes through which the Persians tried to invade Greece the disadvantages that i can see are grief. Especially for the Persian of 480, the persian had to travel a far distance just to invade grace it is a ridiculous amount of time. By then there forces would tired leaving themselves wide open for any possible invasion if there would come forth and once the invasion would commence their forces would most likely be lessoned and weakened in strength and numbers due to the long travel route.. As for the persian invasion of 490 there weakness came from the ships that they deployed due to the surrounds lands known as cyclades (which are all greek islands) around the sea route the persians took it made them easy to spot and invade
