I can't tell if I'm an enneagram 4w5 or 5w4, but I am fairly sure I am one of the two. (Just as background, I am introverted and intuitive but beyond that gave up trying to find my MB type a while ago, and I don't really think actually that there are sixteen types of people, within each of which everyone has the same ordering of the same four cognitive functions.)
On the '4' side, I consider myself very self-absorbed and prone to envy. It seems to me (whether it is actually true or not is besides the point for the moment) that there are certain things, or experiences, that everyone else has, and I envy them for it. My lack of same seems to me an irretrievable loss or absence that makes my life incomplete. Also, I have an anonymous platform where I engage in a lot of self-absorbed chatter about my feelings. And I do long for a 'rescuer' who will understand and accept the secret self that I don't show to anyone else. And I am very, very sensitive. When people criticise something I've done, especially something I've attempted in the creative realm, I feel a need to withdraw, no matter how constructive the criticism is.
On the '5' side, I really hate talking about my emotions with almost everyone. The only contexts under which I spoke about my emotions are 1) under anonymity (where I do it quite a bit), and 2) with someone who appeared, for a time, to be my 'rescuer'. But a site said that if you're unsure of whether you're a 4 or a 5, you should consider whether you're uncomfortable talking about your emotions, and I definitely am. I hate when other people ask me about how I 'feel' (again, except my rescuer). Also, I got the impression that 4s are rather more dramatic than 5s. I definitely do not present emotions around other people, don't really interact with most other people on an emotional level, don't react emotionally to them and don't expect/want them to react emotionally to me. Again, my 'rescuer' excepted.
Also, I don't tend to like to disclose myself to other people, and I've read that's a 5 thing rather than a 4 thing. I only disclose myself (that is, my emotional self) under exceptional circumstances (to my rescuer, under anonymity, or in a foreign language). When I do, though, my expression can become very sensitive, emotional, romantic, etc.
I seem to tend to like 5w4s' intellectual work more than 4w5s' (Nietzsche over Kierkegaard, Kubrick over Bergman).