what are you most known for- uncanny intuition or incredible sensitivity? both types have both qualities, but INFJs will really be able to gain great insight through Ni in particular, and INFPs will really be able to feel all the emotions in the world through Fi.
think of when you first meet someone, do you try to gage their whole personality in one glimpse first of all or do you try to interpret their emotions and feeling toward you first.
also the difference between Fi and Fe is HUGE. i always feel i can tell when someone on this forum uses Fi or Fe a lot. Fe gages on the greater good, whereas Fi gages on the good of each individual. it's strange because often both functions will serve the same use- e.g. a leader being democratic because he cares about each individual's opinion -or- because he feels it will serve the harmony of the group- but at the same time they are wildly different- an Fi person and an Fe person would commonly oppose each other in a court of law for example, a common thing that might happen is an Fi person would feel sympathy for someone's actions because they can see it from their point of view as an individual, an Fe person may feel condemnation for the same actions because they feel it went against the greater good of the group/society.