If you had gotten into Columbia up front, what would you have chosen? It’s hard once you are further down the line to change. Nothing wrong with UND. On the flipside, Ivy is Ivy.
Looking at websites, it seems Columbia is a bit more open to undecided but you might call Notre Dame and see if that’s true…perhaps their website isn’t robust.
As the previous person wrote - you have two great choices. Both are going to get you great outcomes. Since you prefer the bigger city, I’d go to Columbia. Besides, how many people get a chance to spend four years in NYC. It’s an opportunity of a lifetime.