The Symphony has bars. Big Daddy Kane completely murdered that last verse. The Symphony set the bar for posse jams and was the platform for Kane to show the world that he was an elite MC on the level of KRS, Rakim and LL Cool J, who were the hottest MCs at the time.
A Children's Story isn't so much about bars, rather, the focus is songwriting and storytelling.
But the thing that did it for me is the fact that you can play A Children's Story at a club or party and people will rush the dancefloor. The Symphony doesn't have that effect at a party or club.
I voted for Slick Rick.