Judas had lived with Jesus day after day. Peter had been even closer to Jesus. In fact Peter swore that he would never deny Jesus. Both men denounced him, though, and did so right after renewing their commitment to him at the Passover meal!
But let's not be too quick to judge. Even sincere believers who truly love Jesus betray him at times by ungodly thoughts, words, and actions.
Judas felt bad about what he had done, but he did not turn to the Lord and seek forgiveness. Peter did turn to Jesus and found forgiveness. When we "betray" Jesus, let us be like Peter, not Judas.