Basically you have a split between sensing and intuition. Sensing is being connected with a direct experience, i.e. a sensation, there of course is more depth and literature on this but this is basically the concept. Intuition is being less connected with a direct experience, and more so interpolating and "connecting the dots", i.e. taking an intuitive leap. Once again there is of course more depth and literature on this also, but that is the basic dichotomy.
Given this you have Se and Si, and Ne and Ni.... this introduces a further split based on if the perceiving functions are extraverted or introverted. Literally meaning external-facing or internal-facing.
I only mention these pedantics because essentially Ni and Ne are not separate functions but two different variations on a common theme, that being intuition. Ni is no better at "knowing" things than Ne, because this would imply that the external-facing form of intuition possess different qualities than the internal-facing form of intuition. While possible, in order to prove such an argument, one would have to show that internally-facing intuition possesses a greater propensity for knowing things than externally-facing intuition. There is no real argument of this manner beside personal opinion, which is greatly unreliable, who wouldn't want to attribute a positive attribute to themselves.
What I do think is true is the following....
Ne and Ni are similar in nature but different in perspective. Ne is concerned with the outward properties of intuition, being possibilities, potentials, unique defining properties and attributes, and prospects. While Ni is concerned with the inward properties of intuition, being more game theory in nature, like a web of various possibilities, and more temporal and algorithmic in nature. Ne is static because it doesn't have to consider but a single observable possibility in something at a given time. Ni is dynamic because it does consider multiple possibilities in flowing way. The observations made by an Ne ego however are fleeting as these single outwardly manifested traits they perceive are constantly in change. The observations made by an Ni ego however are not fleeting as they are considering more than just a single outwardly manifested trait but rather a web of possibilities.
Ni types may "know" something intuitively but that's not a consequence of their inwardly facing characteristic but more a characteristic of intuition. Intuition is about making intuitive leaps and seeing what is unseen. The actually nature of this "knowing" though is different from Ne types in that Ne types experience more of a single "knowing" event. It's the proverbial "lightbulb" going off in their head, the "ahah" moment, to signify they just know something. Ni types however are more characterized by seeing the various threads of something temporally come together and getting an overwhelming sense of something and knowing it.
All intuitive types are strong in both functions.... however a particular orientation is preferred in the ego, its valued. So that is to say that an Alpha NT or Delta NF doesn't have less perceptual abilities than say a Gamma NT or Beta NF, but rather the nature of these intuitive perceptions is different. To the Ne-valuer this knowing experience is much like a lightbulb going off and to the Ni-valuer it is more so like the clip below (separate threads coming together into a weave of knowing). Also its not uncommon for any intuitive type to experience both attributes, but the ego attempts to prefer and focus on a specific type of experience. Alpha NT's focus on the "aha, lightbulb moments" which may arise from unconscious Ni-based experiences, while Gamma NT's focus on this experience, which may arise from unconscious Ne-based experiences. The fact a single orientation is expressed by the ego allows for duality to exist and there to be a connection between sensory and intuitive functions which is an explanation for another topic. What is important to notice is that link between sensation and intuition... intuition only works by interpolation from sensation. Intuitive leaps are made from disparate sensory perceptions. For Ni... Se sensory experiences are requires to peice together a weave or web. For Ne.... Si sensory experiences are required to experience the lightbulb moment.
A good clip which explains the this weblike temporal nature of Ni is the following, from 1:24 onward... enjoy