What are the advantages and disadvantages of cannibalism?

Well, the advantages of cannibalism can be summarized in one point: The person you are eating is presumably supplying your body with food.

The disadvantages, however, have led to the downfall of entire peoples!

When eating a being of the same species, you are consuming everything that comes with them; pathogens and all!

In other Words, you are putting into your body any diseases that your meal may have had, and as they are of the same species, these diseases will also thrive in you!