I think some advantages to writing your own life story could be:
-You lived it, so you would probably have the most accurate accounts of events that happened during your lifetime
-It wouldn't be affected by how other people might view you and your choices
-You would probably have the most accurate information regarding the people around you
Some disadvantages could be:
-It would take you a long time
-You would have to find a way to get published
-If you aren't a famous person, you might not sell as many copies