The advantages and disadvantages of having four Gospels instead of one single Gospel abound. One advantage of having four gospels includes the stereoscopic depth that would otherwise be missing. In the case of the Synoptic Gospels, much of the material found in one of the Gospels is found in the others. Still, without each of the four Gospels, the picture we have today of Jesus Christ, His ministry, and the early Christian church would be lacking the vividness and completeness we know today. From Matthew’s appreciation for the links between the old covenant and the new and Mark’s quick movement though the action-oriented nature of Jesus’ daily ministry to Luke’s detailed historical survey of the life of Christ and John’s omission of some common details and inclusion of scarce details, the total portrait is more complete and much richer than possible otherwise.
This is not to minimize the Synoptic Problem and other differences found in the four Gospel accounts. The chief disadvantage to having four Gospels lay not in the fact that we have them but rather in the confusion that can surround their relationships with each other. The casual observer can misunderstand this relationship and the average Christian, unfortunately, is ill-equipped to provide a thorough explanation. With so much disagreement over Gospel priority, dating, and even authorship, it is not surprising that confusion exists. Given the difficulty of the issues, there is little wonder that such topics are rarely covered from church pulpits and in discipleship classes.
A sincere question about how to distinguish between the words of Jesus and the opinions of the early church is fair and the average Christian should be able to answer this type of question. If by the question it is meant that there are some things in the canonical Gospels that contemporary scholars believe were not in the original documents, the best way to address this is head on with a firm acknowledgement of the possibility. There are instances such as Mark 16 verses 9-20, known as the long ending, that contemporary scholarship believes are not part of Mark’s original Gospel account. My best advice to a sincere question about such discernment is to seek the answers in prayer. After nearly two thousand years of scholarship on the topic, it is my belief that the answer can only be revealed through the guidance of the Holy Spirit.