As our church has worked our way through the Gospel According to Mark, we have had to come to terms with a number of differences in Mark’s telling of the Story and the other Gospel accounts. On a case by case basis, each one has a reasonable explanation. In terms of the overall picture of this issue, John Piper has a helpful explanation. He says we should view the Gospels as portraits (or paintings) of Jesus and not as photographs:
But in principle I want to say that it helps me to think in terms of portraits. Portraits are different than photographs. Portraits are drawn in order to let the artist make the lips curl just a little bit, like Mona Lisa, so that it says something. And another portrait has the eye tilt a little bit differently, and that says something. And those two things are very different, but not contradictory.
We must remember that the Bible is literature, not simply journalism. It tells a story. God wrote it, and men of distinct style and personality wrote it. Though there are different angles and shadings, the whole thing is more beautiful because God chose to do it that way.