My impression of Ne was that it was more spontaneous. Does that seem to be the case in general?
Often, I think.
I remember something about all the extraverted functions being perceived as apart from the user. Ne is not a way of seeing the self, but of seeing the world...a way of arranging the information -- in this case, intuitively.
The difference between Ni and Ne can thus manifest as it has on shows like House. In many episodes, he has breakthroughs where the answer to a medical problem comes to him when his Intuition is being triggered by outside stimuli. I think that's how Ne is apt to work, and to a lesser extent Ni; Ne is an extraverted function still anchored in the outer world; Ni conclusions and assertions can seem more nebulous than Ne for the fact that, at that point in time, they are nothing but a collective of wispy ideas newly merged in someone's mind. House has been typed as INTP by many.
Ne seems to be more on-the-go (it's an explosive force); Ni seems to require more time (it's an implosive force). This is at least how it's perceived from
outside.
However, Ni is always paired with Se; the two functions are deeply intertwined. Ni can be spontaneous, because it's always being fed by (nearly) unconscious Se. This would mean that Ni could react in the sort of visceral, immediate way we currently think Ne does. ESP skaters, for instance, probably use Ni when they skate and do tricks -- that "gut feeling" seems to arise out of that Ni-Se tandem.
On the whole, though...it's probably that both functions, one Pi and the other Pe, are equally spontaneous, but that you'd never see the full spontaneity of dominant Ni because it's masked by Je.
It also strikes me as analogous to the difference between INTP Intuitions and INTJ: Ji-Ne likes keeping certainties to oneself, and sharing in the possibilities and uncertainties; Ni-Je prefers to preside over the uncertainties in private, and to put on a decided front for all the world.
Consequently, INFPs have
never seemed to like what I guess is my overly judging nature. Unfortunately, I like
sharing my judgments.