Both Threes and Sevens are aggressive or assertive types (PT, 433-36) and both are interested in enjoying different aspects of success. Both types may pursue the acquisition of wealth and status symbols, but with significant differences: Sevens because their sense of self is maintained by possessing things, Threes because status symbols reinforce their feeling of superiority and hence their sense of self.
Sevens love the material world and want to acquire a variety of exciting experiences because having a steady stream of sensations makes them feel alive. They are sensation seekers, whose sense of self is maintained and reinforced by heightening their experience of the world, irrespective of anyone else's knowledge of their acquisitions. For them what is important is the stimulation that the pursuit and acquisition of experiences and things gives them, whether or not anyone else is part of the picture. For example, taking a first-class cruise on an ocean liner is a source of pleasure for Sevens, whether or not anyone else knows that they are doing so. By contrast, unless everyone knows that they are going on an expensive trip and are made to feel envious about it, the experience has far less value for average Threes.
The similarity between Threes and Sevens can be most confusing in the average Levels when Sevens become faddish trendsetters who want to experience whatever is new and exciting right away. (Average Sevens want the excitement of being the first at the hottest place, whereas average Threes are trendy in that they create new status symbols of various kinds for the exclusivity of being one of the "in crowd.") Thus, both types become snobs, with Sevens looking down on others because of the expensive things they have that others do not, and Threes looking down on people because they are able to exclude others from associating with them while still tantalizing them to want to do so.
The differences, however, are very great. The underlying motive for average Sevens is to provide themselves with a continuous stream of stimulation from the environment, particularly from material things. By contrast, the principal underlying motive for average Threes is to rise above others competitively in whatever ways they can—socially, sexually, in status symbols and careers, or simply in their own minds. For Threes, expensive possessions advertise to others that they have arrived socially and that they are desirable–someone others must pay attention to. For example, money allows Threes to hire a governess for their children so they can pursue their careers and so that they can let everyone know that they are successful enough to afford a governess. By contrast, Sevens may engage a governess so that they can travel and not be tied down by having to raise their children themselves.
One of the fundamental reasons why Sevens and Threes are confused in the traditional Enneagram teaching is that unhealthy Sevens in a manic phase have grandiose delusions similar to the grandiose feelings of self-esteem we find in narcissistic Threes. The difference is that Sevens are grandiose about their ability to achieve things: they have great expectations about their activities and plans for the future. When they become manic, everything seems possible for them. By contrast, average Threes are grandiose about their self-worth: narcissistic, exhibitionistic, arrogant and contemptuous of others.
It is likely that these two very different types have been confused because both seem to be narcissistic–that is, inflated with self-love or self-regard. However, average Sevens are not really narcissistic; they may be selfish, self-centered, greedy, insensitive, and so forth, but they do not have an inflated sense of self-worth. Instead, Sevens inflate their desires, appetites, plans, and the glut of their possessions.
Furthermore, by the time that Sevens become grandiose, they are neurotic (at Level 8) and delusionally trying to escape from reality, whereas grandiose Threes are still within the average Levels of Development (at Level 6) and are overcompensating for their fear of failure. The crucial difference is that, beneath their grandiose plans, manic Sevens are intensely insecure and in a flight from anxiety, whereas narcissistically grandiose Threes are not insecure and are fleeing from failure or from being humiliated in any way.
Last, one of the simplest ways to distinguish these two types is by marking the difference in their overall emotional tone and style. Average Threes are cool, in control, projecting the impression that they are perfectly together, with no emotional or personal problems. So convinced of their superiority, they become shameless braggarts and show-offs, arrogantly looking down on others. By contrast, Sevens have many more rough edges, rarely seeming as perfect or as coolly self-contained as Threes. For better or worse, Sevens do not censor themselves and can be funny, outspoken, vulgar, ill mannered, and outrageous–allowing far less polished behavior and attitudes to be displayed for public view. Contrast Sevens such as Bette Midler and Howard Stern with Threes such as Shania Twain and Bryant Gumbel.