I studied Audiology and I have read a few studies on these topics: One thing that could explain the abnormally good score of the 160 VBR is that this is the sound that people are used to. Thus, they tend to rate familiar sounds higher than objectively better ones. On a different note, I wrote my thesis on a somewhat related theme. There, I discovered that different kinds of music indeed performed differently when evaluated for sound quality. Overall trends were constant over genres, but some music showed them more pronounced than other.