So I know a bit about this area (I'm going to a major impact lit org this fall), feel free to PM me if you have questions specific to your situation.
Last year NYU sent 15 students to impact lit organizations. That's not a huge number, but also nothing to sneeze at, given the fact that most NYU students target large firms and federal clerkships, not public interest (and most public interest people target government and direct services, not impact lit). It's also not terribly hard to get a foot in the door of impact lit organizations, given the location, faculty, reputation, clinical opportunities, the competitiveness of NYU students for fellowships, and the school-funded position safety net.
On the other hand, some people targeting "prestigious PI" do struggle to find permanent positions (i.e., positions that aren't fellowships or school-funded). In other words, if you're hellbent on impact lit, you can, as I said, get a foot in the door—do some impact lit externships, clerk at some impact lit orgs during your summers, and almost certainly get a school-funded impact lit position. But is that a guarantee that you'll get hired by an impact lit organization on a permanent basis? No.
And that's sort of the problem with going to law school planning on doing impact lit. The hiring is just so competitive. I truly believe NYU punches above its weight in the PI realm, but it's not Yale. I don't know what the right course of action is here. With Alabama, getting an entry-level impact lit job straight out of law school is pretty unlikely, but at least you won't have any debt to worry about. NYU gives you much better chances at impact lit, but it's not a sure thing, and you'd have loads of debt hanging over your head. I don't think this is a slam dunk decision either way.