Technically? Because the Koran is, word-for-word, the revealed word of God, and the Bible isn't quite that- for example, it can be translated, wheras the Koran can't, because it would then cease to be the Koran. The Bible is sort of the interpreted word of God. (With the proviso that this is my heathen unbeliever take on it.)

But, actually, if I can think of a thing worth putting there, I really will...