NSPU is basically on par with the PVS-502 here. They are both pretty good scopes. The one I think is the mean machine of earlier gen weapon sights is the East German/Czech NSP-2 active IR scope. It doesn't care a bit about other lights, doesn't flare out, doesn't care about how dark the woods are and is has non fisheye vision optics. You think of it like a flashlight, flip it on when you need to look, flip it off when you do not.
I borrowed that one for a night fight in some piss dark woods many years ago and just dominated all the guys with starlight scopes. Sure, they could tell when I flipped it on, but it did not matter because they were dead before they could do anything about it.
I've got an Eltro B8V active scope coming for our West German troops that is rumored to be even nicer, I cannot wait to see that one.