While both of these schools have billion-dollar endowments, they also have large enrollments, and so neither one is particularly wealthy on an endowment-per-student basis. They are not noted for great financial aid; NYU has a particularly weak reputation in this regard. Unlike wealthier schools, neither commits to meeting the “full need” of admitted students:
So if financial aid is "very important", then you may just want to pick the school that gives you the better offer.