By active vs. passive do you mean neutral vs. opinionated in your arguement or do you mean the grammatical definition of those term?
If you mean it in the grammatical sense, you're always supposed to use active (ie. active: The man picked up the book, passive: The book was picked up by the man).
If you're asking about revealing where you stand on a particular arguement, then you want to make sure that you are presenting a well-thouhgt out and balanced point of view on the topic, while addressing all the points they ask you to address.