These types are only confused when NFs, IMO, or perhaps some ISFPs. An SJ, ST or NT 6 just looks 6.
It seems to me, as a four: Sixes have this more heady energy- a lot more anxious and keyed up. It's like you can hear the gears in their head turning. Or there's this sort of nervousness. They seem more either cynical or skeptical (typically 6w5) or trusting and lighter/fun (6w7). They seem more human to me, if that makes sense. Sixes may rebel for the sake of rebelling- for example, shaving their head and getting tattoos just to 'freak people out'. There are a lot more authority issues, or issues with belonging, or issues with deliberately setting themselves apart. Sixes are more loyal and supportive/ desire loyalty and support than fours. They tend to think out loud or tell their thoughts to others in order to process them- the 6w7s, anyway.
Fours have more of a heavy heart energy- this regretful moroseness. When I think of four I think of the first verse of a poem by Paul Verlaine- Il pleure dans mon coeur comme il pleut sur la ville/ Quelle est cette langueur qui penetre mon coeur- It cries in my heart like it rains on the city/ What is this languor which penetrates my heart?
Fours tend to be more sullen or despondent. This isn't to say a four can't have fun and can't be silly, but there's always this undercurrent that the fun silliness is fleeting. Fours are separated from others, but they don't do this deliberately. They just are. They may shave their head and get tattoos but it's more about expressing something within. Fours don't rebel so much as just have a different way of seeing things/ doing things. Others may perceive this as rebellion, but it's not. Fours are self absorbed- by this mean, every thing comes back into the self- how does this affect me? How does this make me feel? How does this relate to my past and me feelings of regret, shame, envy? Fours can also be supportive, but often drop people when the relationship 'feels wrong'. They have higher expectations and become frustrated more easily.
I think this is a good distinction
To elaborate even more...or rather ramble a bit...
One reason why 6s may be more appealing as actual companions (not admired from afar) even when average or unhealthy is that their fixation is more common (Naranjo suggests the 3-6-9 triad as representing the most basic fixations in human psychology and the others as being extensions or secondary to these, which is why these types are most populous). So any neurotic aspect is like the "normal" way to be unhealthy, it's more relatable, understandable, etc. You'll see a lot of self-help and pop psychology frame so much in terms of fear & anxiety. Personally, enneagram helped me identify much of my skewed views & negative behavior as stemming from shame & feeling defective, which is spoken of far less (except in context of abuse). I used to say I could be "timid", but that implies a fear. I don't really fear people at all... I feel ashamed of myself. I hold back myself because I don't want to inflict myself on others. I really don't blame them for rejecting me. 6s seem to worry that others may be mean or dishonest, etc. They seem to consider themselves more innocent and fear some darkness in others - but it's also this projection of their own darkness. When they realize the latter, they still seek to justify it a lot. It becomes some matter of everybody being that way.
6s tend to fear what may be or already is, whether it's in objects, events or other people. They may fear their own faults and resist blame and being detected for falling short of ideals (sort of 1ish there, but it seems more anxious than angry). The focus is on what may be there or what is there. There's a fear of what could happen or what is happening or what may not. To me, 6s can seem paranoid. To them, I seem too into myself to be aware of potential dangers.
6s may feel guilt because they may have taken action or not taken action due to fear, and they see the negative consequences of it. In order to deflect blame, they can play victim. This can give them a martyr attitude. They can be very obsessed with their own worries & bad experiences, which can be self-absorped, but they can present it as informing others of what to fear. They tend to continue to act in the face of this, but it seems to get frantic and less and less relevant to what needs to be done. It's like action for the sake of action, so much worried thought they aren't really digesting anything, etc. It's 9ish inertia through action. Or they can deal with stress by treating reality like a strategy game; they try to keep track of people/things and manipulate them where they want them to be able to control outcomes. They have way more control issues than any 4 will ever have. 4s are only controlling in their creative pursuits (the stereotypical difficult artist), not
6s also have an image connection through 3 - but it's to find security through it. Whether it's being attractive or successful, they seek a security in being wanted/needed or possessing what they need to look out for themselves, not necessarily the kind of validation the 3 seeks. They may try too hard to "be all things", which unlike the 4, means they may lose touch with personal ideals & feelings. I see a lot of 6 women who try to straddle the "tomboy" and "sexy" line. They'll balk if you call them girly, but they'll balk if you call them boyish. They want to be extraordinary to win support of those who have the means to provide it. They get jealous of people who could harm this; they can be far more openly jealous & insecure than 4s (who experience envy very differently). They can become bullies in the name of defending underdogs. Etc...
4s lament.... they lament how short of their ideals they fall, they lament not being seen for who they are, they lament not having the love/significance others have. They lament the past is no longer, they lament the past that was, they lament what the present is not, they lament what the future may never be. The focus is on what is NOT, what is missing. There's a constant grieving over this. But the wistfulness of it makes you heavy... And combined with any refinement at all, it tends to register as aloof, snobby, cool, etc. It's like your mere existence puts a damper on others' happiness (much as a 6's paranoia can rub off). "Misery loves company" is kind of a 4ish attitude, but not cuz we want people to suffer. It can be the only way we know how to connect with someone else. It actually alleviates alienation. 4s can be self-absorped, but then so aware of it that they constantly deflect conversation away from themselves. This can make them seem secretive, and people may complain they are hard to get to know. 4s connect to 1 and can be very hard on themselves & others as far as ideals, and so the snobbery is not entirely untrue. The 4 can seem like a pre-madonna then, something 6s rarely seem like. I'll get tired of people thinking I can be difficult when I'll feel like I've tolerated so much VOID for so long. Like a 1, there can be an angry resentment from that. And the disintegration to 2 can make a 4 seem elitist also; there is a suddenly a pride in their flaws or strangeness, a sense this makes them "special". They may also become seductive, to draw people to them, because there's shame/pride preventing them from going to people.
I have seem elitism in 6s, but it tends to be a group thing (suspicious of outsiders, creating high standards to weed them out) connecting to 3 image, or it's a idealism (ie. Bukowski) that is being threatened, so the person seems to reject everything else. 4s are more lone wolfs, rejecting before being rejected, using an identity of refinement to make up for feeling ugly inside, etc, and elitism is more in the demeanor than the action itself (as the person may be very open to different kinds of people, but not at the expense of their identity, seeming to be unreachable then).
So to recap -
6s - fear what is, what may be, etc, may fear immediate future and take comfort in past/predictable elements or very far-off utopia-like ideal futures.
4s - lament what is not, what has never been or no longer is, what may never be, may have love/hate for the past (bad childhood or good one they miss), take comfort in future hoping for fantasies to manifest, may lament a far-off tragic future should present go on as-is.
So much is clouded by external factors.
Truth lies in the core.
Do you run from fear of being no one, or do you run from fear of no support?
Neither.... I don't run from fear because I don't experience a lot in those terms. Of course I have fears & worries, but it's not an overwhelming fixation for me. I don't tend to run from stuff, but resign myself.
I don't fear being no one.... I feel ashamed of who I am or who I am not. I know I am someone, I just don't feel it's someone who matters to others or someone I myself can even like.
I don't run from this.... I lament & grieve it, and withdraw in the process, alienating myself from people &, well, life. I suppose this might look like running from life, but it's more like stopping in your tracks and lying down to die. It's succumbing to the feelings, not running from them. That's why we will identify with the feelings, whereas 6s tend to project more (or experience them as an outside threat or force, rather than their own psychology).