digital communications - What are the advantages of barker sequence over marker sequnce?

I read that barker sequence is used for synchronization among other uses. Barker sequences are rare and they have special properties - this part I understood. I am missing some thing when I think about how they score over simple marker sequences for synchronization. You want to know where the information bits start - start with a marker sequence preferably which does not occur in the information. And you can synchronize. How do barker sequences score over marker sequences?