A sample library is NOT a real orchestra and one of the advantages forgotten about sample libraries is the choices it gives you regarding sound. Conversely, you could have the same piece of music played by many real orchestras and it would sound different every time.
Fully agreed, as mentioned hereabove, (I quote) "being a virtual (!!) director who is creating and moulding the sound" is what I like so much, working with the top quality libraries anno 2011.