The Gospels of Mark and Matthew while being of the same synoptic tradition contain many differences. Although much of the material is similar we can find many variances between certain accounts of the same stories. There are many theories as to why the stories differ in certain accounts, but the basic reasons for this discrepancy can be discover through critical observation. .
The two authors have reasons for writing different stories and accounts. Both have a message to convey, and both have an audience to speak to. Each Gospel is written in a manner that reflects what the author's purpose is behind the words and stories, as each is trying to do something different with the same original tradition.
Through careful study many theologians have discovered that Mark's Gospel most likely was written first, probably around 70 CE. Therefore most scholars conclude that Mark was a source used by Matthew. Because of this we can contrast Mark and Matthew in a more distinct light, and analyze how and why Matthew would have made certain additions or subtractions. .
The first contrast to look at is the messages of the two Gospels. Mark uses the symbolism of the cross as a representation of Jesus, while Matthew uses the symbol of the Torah. Why the two different symbols? Mark's Gospel focuses on the following of Jesus. Mark tells us we must all pick and bear our own cross in order to follow in the footsteps of our lord. While Mark's Gospel brings us in with its astonishment and wonder, we are dropped of at the roadside half way through being told to walk the rest of the way ourselves.
Matthews Gospel has a different purpose. Matthew reads more like an instruction manual. This directly relates to Matthew's portrayal of Jesus as a teacher. By following the lessons in Matthew we can follow Jesus. This is probably one of the reasons the Catholic Church liked this Gospel especially. It is easier to understand certain messages when they are laid out in this fashion.