Writing an essay on your own is better because you can express your values or display the ideas in your mind which can catch the readers attention. You can think about many things which will help you to gain marks if this is asked in a test. First of all they are giving you tests to understand what you understood in the lesson, if you copy from somewhere else it might help you to get better marks but it will reduce your practical thinking skills and it will help you to develop a negative human value called cheating. So in my point of view it's better to write on your own rather than copying or having someone write it for you.
