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 closed-minded attitude, a determination to be right. In dialogue, one submits one's best thinking, knowing that other peoples' reflections will help improve it rather than destroy it. In debate, one submit's one's best thinking and defends it against challenge to show that it is right.
Dialogue calls for temporarily suspending one's beliefs.
Debate calls for investing wholeheartedly in one's beliefs. In dialogue, one searches for basic agreements. In debate, one searches for glaring differences. In dialogue, one searches for strengths in the other positions. In debate, one searches for flaws and weaknesses in the other position.