So I started thinking about it this way recently: the possible and the conceptual.
There's a simple case for saying Ne is all about the possible and Ni is all about the conceptual. Namely, Ne is (mostly) responsive to environmental cues and Ni (mostly) isn't. Both, formally speaking, are dealing with possibilities and with the conceptual form of things, but Ne sticks much closer to the environment and Ni runs much further from it. So Ne it seems will take more for granted and Ni will take less. Ni necessarily moves into the realm of unattached concepts and Ne sticks with conceptual overlays.
Depth and breadth, suckers.