^ As MB says, supervision and exam essays are completely different beasts altogether. Whilst I am an historian and not an economist, they will be more leniant as to exact quotes- for example, its far more acceptable to apraphrase an opinion in the exams, they don't need exact quotes. Also, I suppose an exam essay would be a lot more strongly argued and brief than a supo one; in teh latter, you've got the time to fully evaluate a topic, evaluating all teh different opinions etc., whereas with teh exam answer its far more a case of argue your point against a few cogent opponents.
But hey, I'm not the best qualified for this, being a mere first year...