Which school of magic do you prefer and why?

Earth and Air are strong and the most "standard" schools. Water is the only school that protects against all sorts of negative effects and can withstand the other three combined, if the army is equal to or stronger than the opponent's (Clone can be even more effective than Explosion or Armageddon). Fire is the only school that can save the game (or rather, the battle) in a hopeless situation.