I think a truly expressive
composer might be better off looking to eventually get their music played by actual instrumentalists.
I don't even think "expressive" when I think of libraries. It's as
@JohnG said, you won't get that with vsts (or at least nowhere near the degree an actual performance of your work would produce).
I think I mentioned in another thread, there will never be a sample library that can match a soloist or ensemble for real, one whom knows your music inside and out for performance, heeding your input until you're satisfied. Even better, one that actually
likes the music they're being paid to play (this last I learned with my own music...if they love or even really like it, it will be astonishing, if they're noncommital it will be professional, if they hate it it will still be better than using libraries).
I think HZ said it well: "there is no such thing as an orchestra in a box". There are however great sounding libraries that can be really inspiring and work terrific...toward making mock ups.