I would like to come back and read the rest of this thread later, but yes, I believe the distinction is important. After leaving a very fundamentalist Christianity, I didn't come back to study my religious roots again until around four years ago and have come to new conclusions.
The Christ story most definitely evolved. The writer of the gospel of Mark didn't seem to know about the Virgin birth. In some translations of Mark 3:20-30, Jesus' family, including his mother, doubted him, thinking him mad. Why would a mother who gave a virgin birth think her son was mad rather than divine? Paul never mentioned the Virgin birth.
The four gospel accounts of the resurrection evolve drastically from the earliest gospel (Mark) through the latest (John), becoming more and more extravagant and detailed.
The Christ story continues to evolve with each new generation of people who believe in him, Christians or not (Muslims and the Baha'i faith and others recognize him, too.) The legend grew with time. The post-Eastern Christ of Christianity, resurrected and divine, is a mythic, not historical Christ.
The problem with those of us in the modern West is that we are so caught up in logical thinking because of the enlightenment (and don't get me wrong, logic is vitally important) that religious and non-religious alike are often not able to read a myth and appreciate it for what it is. Instead, they often read it as literal history and either accept it or reject it.
Myths are important for what they are. They are not literal history.