One of the best ways to analyze any passage of Scripture is to use other Scripture. In both Ezekiel (chapters 1 and 10) and Revelation (chapter 4) four angels appear to the respective prophets in a form that mirrors the four gospels. One has the face of a lion, as Matthew presented Jesus as King of the Jews, the Lion of the tribe of Judah. Another has the face of either a cherub or an ox, a servant (of God or man), as Mark presented Jesus as servant of both God and man. The third angel has the face of man, as Luke presented Jesus as the Son of Man. The fourth angel has the face of an eagle, symbol of divinity, as John presents Jesus as God incarnate.
Thus, when Mark describes the last supper Jesus had with His disciples, his focus is on how Jesus is serving the men who will soon abandon Him to the Romans. When John wrote his description of the same scene, the scene and events were the same, but his focus was on how Jesus manifests the characteristics of God.
In both cases, Jesus needs to keep the Passover, as He has for over thirty years, as a faithful and obedient Jew. This time, however, there was a conspiracy between one of His disciples and His enemies, the Pharisees. With hindsight, Mark describes the scene in Bethany first, showing how Judas revealed his hand (Mark 14:3-9), though no one else but Jesus noticed at the time (Mark 14:18-21). As their servant, Jesus comforts the disciples by telling them what will happen, so when it does happen they will know that though He was the servant of all (Matt. 20:26-27), He was always in control.
In John's account, he gives more detail with more focus on what was happening with Judas, perhaps because by 90 a.d. some had begun, as is true now, to sympathize with Judas. John describes how Judas let Satan influence him and into him (13:2, 27). John also was writing after the church was a well-established entity so he included a speech of Jesus' that Mark did not believe necessar...