I have never tested the VA-7, so I can't comment on it.
Piano would go to Yamaha; High quality, low volume. When you say strings and brass, If you mean ensemble voices, then I would go with Roland on those. If you are referring to solo brass and string voices, then the Yamaha sweet voices, in those categories, are unbeatable. The PSR3000 has more guitar sounds then the EXR7 and they are very good.
Starkeeper