The question is what is the advantage:
1. To be a Jew?
2. To be Circumcised?
Paul being a Jew is writing to his buddies. To his friends that probably are having a hard time understanding why he became a Christian. He is going to answer the question Why God made him a Jew, and why he is circumcised, and ultimately share about his jewish heritage and what it means to be a jewish christian.

Romans 3:1