Hey! So... keeping in mind that it is impossible to really understand the inner world of other types, since it is something which has to be experienced to be understood, I feel I can shed some light on this topic. I have been best friends with a male INTJ for going on 10 years.
INTJs and INFJs can talk for hours and hours and never get bored. We both use complex and seemingly ambiguous modes of thought, so we get each other. Most people miss much of what I say, but the INTJ sees the connections I'm making (which is a really good thing because when INTJs think you have flawed reasoning, they merrily bludgeon you with it).
The chemistry is very stimulating and compatible for the most part. We're both comfortable not discussing emotions and menial details about life. We don't get uptight or hold grudges because our inner worlds are waaaay too intense to deal with interpersonal drama. He is absorbed in perfecting his thinking, formulations and judgements, and I am totally wrapped up in intense feeling, collecting aha moments and labeling things good or bad. We both enjoy developing intense and complex abstract ideas, so we never run out of things to talk about. We're also both pretty evenly matched power-wise in the conversation.
The differences are huge, though!!!
I'm romantically and passionately drawn to people, personal growth and empathy. I can be engaging and warm as long as I don't have to compete for time. I'm frequently confused by peoples' interest in things that can't save the world, so I often get quiet and just pointed one-liners (which are usually unnoticed) or just reflect my empathy for them. I don't like to talk about my interests with people who don't get it, because unity is more enjoyable to me. I'd rather write books, songs and make paintings so they can choose to be benefited by my ideas on their own timetable. Seemingly out of character, I sometimes accidentally boil over into a passionate diatribe, which really confuses people since I'm normally super self-effacing and even-keeled. I've lost many acquaintances this way. But really I'm just trying to change their mind about something to prevent them or someone else from getting hurt.
The INTJ is an orchestrater and a laid-back comedian, sometimes stepping on the toes of others with critical statements or insensitive humor which people forgive him for due to his intense charisma and genuine goodwill toward others. He is a self-contained unit emotionally, but he relies on social interaction to get his inspiration flowing and to throw various data at him to ponder over. He also loves having a bouncing board, which I understand because ideas can get pretty complex and chaotic when you live in a world of abstractions. Although he can off as rude or antiseptic at times, underneath it all he has intense goodwill toward others, so he has many loyal friends and great relationships with family members.
In some ways, both INFJs and INTJs are socially charismatic and inspiring, and they can both be overwhelming when they speak from the heart, which is why we don't do it too often. Also, both INTJs and INFJs have the interests of other people at heart and they both (arrogantly) believe that other people would be better off if they would embrace our knowledge.
The INTJ is more interested in obsessing over the information itself to refine a perfectly objective mind to improve the objective world, whereas the INFJ is busy obsessively reading people to understand the variations in the human element, which is the only way to create large-scale solutions for large-scale groups if you want to include subjective solutions as well as objective ones. It is quite difficult to harmonize the discrepancies between subjective and objective truth, which is why INFJs often seem to be a conundrum, and it takes a lot of focus to rationalize so much while talking to people to gain understanding, which is why we're often misconstrued as ditzy or 'off'. The INTJ doesn't so much bother with the subjective stuff (all his subjective truths are objective, LOL!), so he seems vastly more put together until he goes off on a tangent about conspiracy theories, that is.
The INTJ sees himself as a bearer of truth. He sees the world in terms of true and false and believes he can singlehandedly deduce anything using systematic logic. He never talks about his feelings, so I can't tell you much about that aspect. The INFJ is almost always overwhelming caught up in a tide of feelings and profound meanings, and when I communicate with others I can hardly see them for who they are through my cloud of thought. Some see me as emotionally detached, and I am, but only because I feel so much for them that I have to keep my emotions tightly reined in just to function and actively problem-solve.
The INTJ is not bothered by conflict or relational issues. He deals in logic, not subjective truths. His dealings with people focus on tasks and black and white truth. The INTJ doesn't seem to get drained in social settings as much as he gets bored. As an INFJ, I am unbearably disturbed by relational conflict. So much so that I spend much of my time hiding behind closed doors, or at least hiding any part of myself that isn't theoretical or abstract (similar to the INTJ). I hide my needs and focus on others. This is a summary for why I get drained in social situations.
The one warning I would give for relationships between these types is that if the INFJ gets disrespected or feels useless, or if the INTJ gets disappointed in her or feels neglected, the fights can be complete and total meltdowns, and it is fairly easy for both types to pack up and move on with their lives.
[Note: If you know any INTJs, you know that my friend would abundantly critique every observation I've made about him, so you may have to ask and INTJ for a true insight into the matter
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Sorry for the long post, I hope that is helpful!
