A blend of both. Classical music has strong emotion, and great musical background, while rock has the instruments to bring great drama very quickly.
If anyone reading this haven't ever heard of David Garret, go look up one of his songs RIGHT NOW. It's exactly a perfect blend.
that I happened upon while reading up on something called the Tritone or Diabolus in Musica and is what gives this music it's power. This is Karl Jenkins' version of the Dies Irae Requiem. It is interesting to note that many Metal bands use the Tritone to good effect.