Delphi oracle and ancient corinth both are in UNESCO World Heritage Sites. With this experience you cover the chapters from 900b.c. Greece civilisation until 150a.d. Roman civilization and the huge change in world religion with Saint Paul with his letters and his speech in Corinth.
Αpart from the historical interest, you will have the opportunity to admire the Greek nature, the mountains and the sea, but also the Greek cuisine.
There is no other tour that you can visit both important sites in one day.