We asked 6 CPEs (people who have successfully passed the Cambridge Proficiency in English exam) and this is what they said to us:
CPE1: "An article is a piece of writing where a topic, either serious or light-hearted, is tackled from a personal point of view, including personal experience or arguments. Its purpose is generally to both inform and entertain. On the other hand, an essay is a piece of writing tending towards the academic: the topic in discussion is of a more serious nature and the writer is expected to provide an idea plus the arguments that discuss it. In doing so, they will have to refer to specific points about the issue in question and will generally have to use more precise language."
CPE2: "Article, informative, based on facts. Essay, develops an argument, involves opinions (so does a for an against article, oops!)."
CPE3: "As far as I´m concerned essays are more academic, you need to analyse both sides of the topic, and provide arguments to back you up, whereas articles are somehow more flexible and can have a more neutral tone."
CPE4: "I think an essay develops arguments and has always your opinion. An article gives information, although sometimes you can write your opinion."
CPE6: "Well, I think an essay is normally more academic and analytical, when the writer supports his views usually has to make reference to factual information and other people's or authors' views and findings. An article is basically aimed to inform or entertain the reader, it can be formal or informal depending on the topic and publication it appears whereas an essay is rarely informal. An article is published mainly in magazines or newspapers, for example a school´s newspaper, while an essay is normally a university assignment. Some essays might be of more than three pages, but for international exams we have to keep them short. The tone of an essay is generally serious, compared to the one of an article which might sound more relaxed and include some humour. I hope I have contributed with something."