I have simply answered directly from the notes, which i read and meditated on mosy of yesterday. Isn't it wonderful how God gets your attention!
Slave: "one who is solely committed to another, "slave, subject," denoting "compulsory service." ie "slaves" are committed to their Master for life.
Saint: "the holy ones, saints," as consecrated to God. ie believers are dedicated, set apart to the service of God.
Being a "slave of Christ Jesus" and being a "saint" of God are pretty much the same thing, just looking at different aspects of belonging "lock, stock, and barrel" to God!