The authors of pro & con or biased articles, books, or other sources have a specific bias and are trying to persuade the reader of a specific point of view in contrast to most academic articles that typically focus on topics in an objective manner that is meant to inform the reader.
Here are some characteristics of persuasive or biased articles:
Opinion or pro & con articles, books, or other resources with bias are ideal to use in argumentative papers or presentations.
They can also be used for informative research assignments, but you have to be more careful so as not to produce an unintentionally biased paper or presentation that is meant to be objective.
Most importantly, you have to be able to recognize if your source is biased and if it is appropriate for your assignment. If you aren't sure, ask your instructor.