Spot the Difference

The statues are called caryatids, and these two are the real deal, in the Acropolis Museum in Athens.  Their copies are on the Acropolis, where the original six sisters originated.  They are not part of the Parthenon, rather they are part of the temple called the Erechtheion, which is near the Parthenon.

A caryatid is used instead of a pillar or a column, to provide architectural support.

One of their sisters is in the British Museum, with the Elgin/Parthenon Marbles.