Fi focuses on exploring feelings, values, and needs--a sense of importance--rooted in one's own ability to RELATE. It draws from one's own direct experiences, as a kind of value/emotions/needs map that helps them summon up a quality of presence that appreciates what it's actually like to experience something, the deeper qualities that characterize it and/or the path through experiencing it. This is partly why they often have a wonderfully attuned sociological awareness.
Fe is different. We focus more on objective perspectives and take snapshots that we compile into a strange, fractured but seemingly whole overview (as opposed to the wonderful deep cave analogy given by magpie). So instead of direct experience, we are building foundations on what assumptions we most trust to help us see what is going on. The focus then is more about cultivating intentionality, in fostering a quality of integrity that holds together our way of being ourselves into something good, something with a healthy outlook and with a resolute perspective in staying the course towards that (a kind of attitude intelligence).
This sense of prioritization is where our values lie, as we imagine them in a world in which we step back, push-play, and appreciate the goodness in the way that it circulates through our interactions and ways of being together, more than in terms of the Fi way of knowing that at the deepest level we are in alignment with our own needs (and being gracious in allowing and giving space for others to explore themselves to find that as well). As Fe users, examining ourselves directly, our experience more directly can be difficult and takes some time to learn to fully complete the loop and do the whole thing outside in and inside out. I think this blind spot is very similar to the one peacebaby mentions for Fi users, when she seems to be discussing the ideological sleight-of-hand that Fi users can do when they don't check in with the empirical side of things, the side that says not only measuring something from my own perspective but appreciating the aggregation of perspectives can sometimes be helpful in holding steady the different things that are getting in the way of hearing the other things.
Both feeling functions bring about an ability to listen deeply (and wholly) and to appreciate conflict, beauty, healthiness, expressive (personal, embodied) truth, and peace.
edit to add:
good Fe, I think, is attentive to the seeds we plant and their systemic consequences. good Fi, in contrast, seems to be attentive to the way truly listening to our own needs gives us space to CHOOSE while appreciating the importance of that freedom (with a corresponding and right belief that when you learn how to get out of your own way, caring and creatively committing to the good just happens, in part because we have such strong need to connect, to belong, and to meaningfully contribute to others).