David's voice is indeed superiour, but his singing style on songs like SOYCD is terrible, in my opinion. He simply can't reach the notes, and that's very audible. Not to mention that he can't put emotion into it, something Roger is very good at.

That's something I hear in almost every song David sings which was originally sung by Roger, by the way. They really knew what they were doing when they chose who would sing which song, and these decisions always had important reasons, musically. Roger's voice and singing style is suited for songs like SOYCD way more than David's, because David's is more soothing and gentle. As I've said before, that's why Roger doesn't sing on their earlier soundtrack albums - his voice catches the attention too much and isn't precise enough for film music.

Just imagine Roger singing Cymbaline or David singing The Gunner's Dream; you'll understand exactly what I mean. :)