Both are good in Econ (undergraduate level).
Both should have no problem sending a deserving kid to Wall Street or consulting.
NU tends to have more kids from richer families.
If a kid is aiming for Econ Ph.D eventually and working in academia, UChicago has a slight edge (for undergraduate studies in Econ).
Chicago Econ is no longer as strong as before. It now trails MIT, Harvard and more recently even UCB, Stanford and Princeton.
However, it got a large donation recently and it is expected to regain some old-time glories.