This thread really could go in any general personality forum and can be discussed easily with no mention of letters or numbers, but I'm going to put it in Enneagram because that is where I spend most of my time and am most interested in.
Anyway. What holds more weight in reading someone's true personality: how you are at home or in casual situations with friends and intimates, or how you carry yourself at work and/or school? Or, both or neither, especially seeing as some types develop bigger work/home life splits in their manner than others? The common meme is that you should go by how you are when you are free to let your hair down, but I'm not sure. How you face a system and choose whether and how to work within it speaks a hell of a lot about your character, IMHO (Hmm...what is the relationship between personality and character?). For instance, you could have two twin sisters who are equally outspoken and aggressive among family members, but when they go off to high school, one of them clams up and quietly follows the rules, and the other one remains a rebel wherever she goes. Something is essentially different between these two.
Of course, this raises the old question of how much behavior means.