I'm interested in behavioural differences between the two types. Any takers?
I believe both the INTJ and ENTJ (disregarding the 'E' and 'I' extremes) are highly similar - because of the 'NTJ' function. Both are well-apt in leadership, getting things done and making good careers.
... The only difference being is that the ENTJ takes a more explorative approach to the 'problem' (hence the term, Executive) and the INTJ takes a more insightful approach (hence the term, Scientist).
Normally, I get INTJs and ENTJs on my personality tests - with slightly more ENTJs, and normally extraversion more prominent than introversion by the percentages. I'm an NTJ that tenders more on extravert. I feel that is right, as I could be explorative as well as insightful to situations.