Not only did Peter and Paul preach gospel messages that had different names and different audiences, but the content, the substance, of what they preached was different also. The content of Peter’s gospel focused upon the identity of Jesus Christ and the fact that the Messiah was on the scene ready to bring in the prophesied Kingdom. The following are examples of people BEFORE the calling of the apostle Paul (and his gospel), and their response to the gospel that was being preached to them:
[John 1:48-49] Nathanael saith unto him, Whence knowest thou me? Jesus answered and said unto him, Before that Philip called thee, when thou wast under the fig tree, I saw thee. Nathanael answered and saith unto him, Rabbi, thou art the Son of God; thou art the King of Israel.
[John 11:25-27] Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live: And whosoever liveth and believeth in me shall never die. Believest thou this? She saith unto him, Yea, Lord: I believe that thou art the Christ, the Son of God, which should come into the world.
[Matt 16:15-16] He saith unto them, But whom say ye that I am? And Simon Peter answered and said, Thou art the Christ, the Son of the living God.
[Acts 8:35-37] Then Philip opened his mouth, and began at the same scripture, and preached unto him Jesus. And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God.
What is demonstrated within the examples above is faith in the identity of Jesus Christ. This is referred to within the four Gospels as believing in the name of Christ the Lord: