Here is Pope Benedict XVI describing why the organ is better than guitars in worship:
The organ has always been considered, and rightly so, the king of musical instruments, because it takes up all the sounds of creation – as was just said – and gives resonance to the fullness of human sentiments, from joy to sadness, from praise to lamentation. By transcending the merely human sphere, as all music of quality does, it evokes the divine. The organ’s great range of timbre, from piano through to a thundering fortissimo, makes it an instrument superior to all others. It is capable of echoing and expressing all the experiences of human life. The manifold possibilities of the organ in some way remind us of the immensity and the magnificence of God.
Okay, he’s not directly contrasting with guitars, but it’s probably in his mind after a few too many hokey John Paul II masses.