In debate, winning is the goal. In debate, one listens to the other side in order to find flaws and to counter its arguments. Dialogue enlarges and possibly changes a participants point of view. Debate affirms a participant's own point of view. Dialogue reveals assumptions for re-evaluation.
Debate defends assumptions as truth.
Dialogue causes introspection on ones own position. Debate causes critique of the other position. Dialogue opens the possibility of reaching a better solution than any of the original solutions. Debate defends one's own positions as the best solution and excludes other solutions. Debate creates a close-minded attitude, a determination to be right.