I think it is valuable to signal agreeableness in most but not all contexts; in the context in which Steve Jobs worked it might have been valuable to signal disagreeableness to enhance an impression of brilliant iconoclasm. Privately, it's probably a bad idea to think of yourself as either particularly agreeable or particularly disagreeable; the extent to which you agree or disagree with people in private should vary a lot more than either of those adjectives suggest (depending on who you're agreeing or disagreeing with). I don't have an answer to your actual question, though.