Question

A major difference between "classical" Greek art and the art of the Hellenistic era was

Answer 1

The Classical period of Greek history lasted from the late sixth to late fourth centuries B.C., ending with the death of Alexander the Great in 323 B.C. Following Alexander's death, his empire fragmented into competing kingdoms ruled by his generals and their heirs. This period is known as the Hellenistic period and lasted until the middle of the second century B.C. Art from these two periods has many similarities, but also many differences.

Answer 2

I'm assuming you're talking about Greek sculptures. While both Classical and Hellenistic sculptures were mostly idealized, meaning they did not depict humans as they actually were (imagine photoshop but sculpting people instead of photoshopping them), I would say a major difference was that Hellenistic art was more detailed and had more emotion to them, while Classical statues had blank expressions.