"Naturally it [difficulty observing type] depends very largely also upon the attitude of the observer, whether he lays hold of the conscious or the unconscious character of a personality. Speaking generally a judging observer will tend to seize the conscious character, while a perceptive observer will be influenced more by the unconscious character, since judgment is chiefly interested in the conscious motivation of the psychic process, while perception tends to register the mere happening." (Psychological Types, 427.)
So Judgers tend to "lay hold of" the conscious, that is, the superior, or conscious, dominant function which motivates or drives a person; while Perceivers register behavioral actuality which creeps up from the unconscious ego, representing functions that the person is not completely aware of or in control of.
I used to make various observations about my 8w7 ESTJ former boss, who is quite the man's man and completely in charge of his external realm of activity. But external control and - in his case - domination, is implicitly about controlling the subconscious, or unconscious, subjective factor.
As a result, his actual behavior, as I observed it, was entirely childish for a man's man such as him. He was childishly selfish, and he had the 2-year-old's greedy attitude of "mine! mine! mine!" His entire personal world was ego-dominant. And he used to "play" with other people like they were his toys. If he was bored, he would create problems, while pretending to be completely innocent of everything, and then order his employees to clean up the messes while blaming them for it all.
If I were a Judger, these things would not register with me. Judging is something I've developed through personality theory. Perceivers, I've found, don't understand my judgments about personality issues such as motives which Judgers are instinctively aware of. An untrained observer of human behavior doesn't understand, and becomes a victim of Judger motivations they can't comprehend because they, as every untrained person, assumes everybody else's thought-patterns match their own. Thus the average Perceiver is left standing flat-footed while the Judger, who instinctively understands motivation and thus can gain control over humans through their various motivations, runs circles around him.
That's not to say that Judgers are always right, instincts are not omniscient. But if Judgers are right more often than not in their instincts about what drives people, then they can gain the upper-hand more often than not.
The Perceiver doesn't think in such terms. Judgers ruined my childhood. Judgers are intensely competitive at games, while I played them for fun. Winning or losing didn't affect me, I was interested in observing the outcomes. For some reason, this makes Judgers extremely angry. Whenever Judgers became involved in sports I was active in, they ruined it for me because it stopped being fun due to the constant pressure to succeed and win. They didn't see me as motivated by perception, but only the fact that I was not driven enough by their motives to take it all so seriously. Of course I realize we had different ideas about the concept of "fun." "Fun" to me was playing the game, "fun" was in the "journey" and in observing the outcome; "fun" to them was plotting how to win and then winning the game.
Since, for me, outcomes are objective, these outcomes are spoiled by any cheating. For Judgers, cheating was part of the game. As an example, my former boss, who would cheat anybody at any time; and even if he lost in the end, the fact that someone else got cheated made it all worthwhile. I literally observed him clap his hands together once and then start rubbing them together in glee, grinning as if he was some villain in a "b" grade movie. I watched as he falsified his computerized business records in order to cheat some Israeli businessmen out of a mere $5000, which to him is chicken feed, simply in order to win a contract which others were competing for. Money wasn't the motive, winning was the motive.
We disagree on type calls because we focus on different elements of a personality. Judgers focus on motives, while Perceivers focus on behaviors. I've described personality in this post which to me is mostly a behavior, by instinct. But due to personality training I can delve down to the motives, it just doesn't come as easy to me.