Well first we can see similarities, one already stated that they both were part of the 12 apostles that walked with Christ, but they also both betrayed Christ. Peter denied Christ three times and declared that he did not know him. Judas conspired with those that sought to crucify Jesus for money. Christ also predicted both of these incidents telling Peter that he would deny him, and telling Judas to do what he must do quickly.
However there is a clear difference in the way Christ approaches and sees Peter and Judas. We see this difference within the similarity above because even though Christ predicts both betrayals he tells Peter that he will be praying for him. We see this in Luke’s account chapter 22:31 where Jesus says “Simon, Simon, behold, Satan demanded to have you that he might sift you like wheat, but I have prayed for you that your faith may not fail.
So what is the prayer of Jesus like? We see an example right after this encounter with Peter but before His arrest. It is called the high priestly prayer of which I have taken some excerpts from as follows. John 17:6(ESV) – I have manifested your name to the people whom you gave me out of the world. Yours they were, and you gave them to me, and they have kept your word. Verse 9 – I am praying for them. I am not praying for the world, but for those whom you have given me, for they are yours. Verse 12 – While I was with them, I kept them in your name, which you have given me. I have guarded them and not one of them has been lost except the son of destruction, that the scripture be fulfilled.
It is clear I think that the difference between Peter and Judas primarily is that Jesus prayed for Peter as he told him he would and there was no prayer offered for Judas. It is also clear that all that were given by the Father were kept and that Judas was not, specifically for the purpose of the fulfillment of prophecy. Judas was not kept and then lost, but Judas was always lost or “destined for destruction” as the Hebraism goes. Judas was part of the “world” that Jesus says he is not praying for and is therefore sifted like wheat as Peter would have been had Jesus not interceded for him on his behalf.
Later in the prayer Christ includes all those who will be saved that are also given of the Father because of His love for the Son before the foundation of the world. Further clarification is given in verse 25 where Christ says “O righteous Father, even though the world does not know you, I know you, and these know that you have sent me.” It is for this reason that one day Christ will say to those who reject him “depart from me for I never knew you”. Christ does not lose who the Father gives and unless the Father gives He never has a relationship with you.
The difference between Judas and Peter and the prayer of Jesus himself to the Father before his sacrificial death helps us further understand the triune relationship between the God head and to man and how God is glorified from it.