I wrote this in Megan's ISTj thread in Beta --

"Easily and quickly" --

The ISTj, when voicing his opinion, is more likely to make "to the point" and clear statements, "this is so", while the ESTj is more likely to sound more flexible, reasonable or, to some, "insecure".

The ISTj is more likely to seem calm, unflappable, someone who will keep his head in most situations - unless in periods of extreme uncertainty, when he will seem extremely agitated and a nervous wreck. Very little in between. The latter is rare, though.

The ESTj is more likely to make a restless impression, someone who can't seem to be able to stay quiet for long, a "I should be doing something" feel.

The ISTj is easier to picture as an inspector, policeman, or soldier. The ESTj, as a boy scout or middle manager.

The ESTj is more likely to either need a very rigid schedule and follow preset appointments - or tend to get focused into what needs to be done at the moment and lose track of his schedule. The ISTj dislikes putting things off, but he's more comfortable with working without a preset schedule.

The ISTj man (women are different) is likely to present a mostly low-emotion personality most of the time, but he can "let go" in social occasions or when enjoying a joke or very angry. The ESTj is more likely to present a polite, friendly but very slightly shy persona most of the time, and not "let go" like the ISTj.