I have notcied the differences in 1. the women, Matthew, and Mark mentions both Marys. Luke mentions both Marys as well as other women and john only mentions 1 Mary. The number of Angels present differs from 1 to 2. Each writer gives more detail then the other.
When I look at the differences between the witnessses I look at as if a person would an auto accident. The person or persons involved as well as the witnesses will tell the same story but in a different way, some with more details some with less and some might see it from a different point of view, but the end result is the same.
The credibility is the fact that each person has exactly the same story to tell, even with the differences the similarities outway it. They each have the same message. Jesus never changes in the accounts. His love and compassion is still evident.