What is he interested in studying?
Sibling may help at sibling’s Ivy.
Social depends on the kid. Either can be great for the right kid. How does he feel about being in the South? How much does he like being near NYC?
Did he visit both campuses?
Academics are very strong at both schools.
Most people would choose Princeton, if admitted to both, but his odds are probably better with Duke, if he has no hard hook.
Princeton scrapped the grading curve, which is a plus.