Fe Extroverted Feeling relates to Communicating harmony through expression. Fe users, will smile, not because they are happy but because its the acceptable reaction to the group. Most Fe users wear their emotions and feelings and are easy to read. When someone tells someone else to "Smile!" its typically a Fe user. Harmony is big driver to a Fe dom user. (ESFJ, ENFJ, INFJ, ISFJ, ESTP, ENTP, ISTP, INTP)
Fi Introverted Feeling is about being Authentic to one's self and expressing Genuineness. It values things based on rightness and wrongness to the self. It deals with emotion internally, what you see from a Fi user is what they let you see. When someone says, "Be Yourself" its typically a Fi user. Being (ISFP, INFP, ENFP, ESFP, INTJ, ISTJ, ESTJ, ENTJ)
I'm both of these things depending on what the particular situation requires in context; depending on my focus, aim, and intuition. My life often feels like a finely tuned balancing act between the need for expression or the need for lack of it. And sometimes it's out of politeness, other times it's out of some form of necessity. Sometimes I'm expressive to assert a stipulation and other times because of some other reason.
Every situation is different. I can't say i'm predominantly one or the other, because everything has a certain context and requires a certain response or motivation.