I found this while lurking on the internet. I don't know how accurate it is, and it's kind of long, but I think it may help all of us lovely NFP ambiverts decide once and for all!
P.S. If any of you have any questions, I'd love to help you find your type. It's one of my favorite things to do. Meanwhile, I'll spend more time trying to figure out my own ENFP vs INFP conflict. :P
"I think one of the key differences is how the types react to conflict. Both types hate conflict, but they’re going to react differently when faced with it. In general, the INFP will withdraw. She will retreat into herself, seeming aloof and distanced. The INFP has a deep need for peace and harmony, especially within herself. She will go to great lengths to protect that harmony. The ENFP also values peace, but will react in different ways. During conflict, the ENFP may retreat, but is more likely to try diffusing the situation with humor. When uncomfortable, the ENFP may throw up the classic ‘goofy mask’ as a defense mechanism. The INFP is less likely to use this silly façade in the face of conflict or discomfort.
Another key difference is how private the person is. Introverts, in general, are harder to get to know as quickly as extraverts are. Both INFPs and ENFPs have rich inner lives, but the INFP is likely to be much more guarded—not as keen on talking about themselves. ENFPs lead with Ne and auxiliary Fi. INFPs lead with Fi and auxiliary Ne. The INFP will take in information and then keep it inside their beautiful inner ‘treasure chest’, if you will. The ENFP will take in the information and let it bubble out in a fountain of enthusiasm.
The INFP is more likely to be called sweet or mysterious. The ENFP is more likely to be called enthusiastic or bubbly. (Keep in mind, however, that both of these types love to dream. They love the mysterious and archetypal.)
I think probably the main reason the two are confused is because ENFPs don’t always come across as stereotypical extraverts. They can be like chameleons—they can seem like INFPs, ESFPs, maybe other types, too. ENFPs usually do need some time to themselves to sort through their thoughts, more so than any other extraverted type. This can cause confusion in the introvert-extravert category. In my own experience, I’ve noticed one way to tell between an introvert or an extravert. Introverts will know beyond a shadow of a doubt that they are introverts. They need to be alone, spend some time away from the world, and recharge. Recharging will be something they look forward to very much. Their “me” time is very crucial to their lives. Extraverts, especially ENFPs, may initially be very unsure of whether they are introverts or not. If you’re unsure, you probably lean towards extraverted. Think about how you feel after spending a night out with your best friends. Introverts will probably feel the need to go chill and do something alone to feel refreshed, even though they had a great time. As an extravert, I get this sort of “buzz” after spending time with my good friends. I come home and feel great and full of energy. After spending a whole day all by myself, I feel sluggish and irritable.
Also, what do you do when you’re faced with a choice or a problem? I’ve noticed that many introverts tend to retreat into their brain space to figure out the answer. Extraverts, including myself, tend to talk it out with several people.
INFPs and ENFPs are both quirky and unusual. INFPs are usually a little more of a subdued, mystical kind of quirky. ENFPs are quirky in a more bubbly, enthusiastic way.
The ENFP is probably going to be more initially open than the INFP.
ENFPs need more alone time than most of the other E-types.
INFPs tend to retreat during times of conflict; ENFPs will attempt to ease the situation (and possibly their own anxieties) through humor and goofiness.