It's important that we get Jesus right. John 10: 30 is one of many references where Jesus declares his oneness with God the father. What do we lose if Jesus is not God? To deny the deity of Jesus is to imperil our eternal destiny.In John 10 the religious leaders peppered him with questions, the main one being, "Are you the Christ? If you are, tell us plainly." Jesus reminds them, "Even if I told you, you would not believe me" (John 10: 25). The inability to see Jesus as the Christ, the Son of God, stems from spiritual blindness. Without spiritual rebirth, that only Christ can provide, they couldn’t believe. This is was not a mere flight of logic. So they were in a catch 22: in order to see Christ as God they needed to believe in the One who was standing before them; but as long as they rejected him they would never know him as Son of God.
This is why Jesus said, "My sheep hear my voice, and I know them and they follow me." Knowing Jesus as Messiah and God is to be in a relationship with the Great Shepherd who saves and keeps his own sheep. Then to validate his claim as God in the flesh, Jesus said, "I give them eternal life, and they will never perish and no one will snatch them out of my hand" John 8: 28. This is one of the great promises of Scripture: we are eternally secure in Christ. Jesus gives eternally life to those whom he chooses.
Jesus then refers to his Father as having the same power that he has to save and protect his children, "My Father who has given them to me is greater than all and no one is able to snatch them out of the Father's hand. I am the Father are one." These were fighting words to his enemies. Jesus' words thus amount to a claim to deity. Hence, the Jews pick up stones to put him to death. Jesus was not a mini-god, or a part of God. Jesus is one in essence and substance with the Father. The Nicene Creed (328 AD) is clear, [Jesus is] very God of very God, begotten, not made, being of one substance with the Father.
So here's the theological question: What do we lose if we confess Jesus as less than Son of God?