dsilver, the two demos I was thinking of (but was not remembering) are two demos under the "strings complete" package. The two are "Irish Strings" and "Compare Rag". Both feature the same material being played first by solo strings, then chamber, then orchestra, and last, AP Strings. They give a very good comparison of the basic sound of the four different libraries.
They demonstrate fairly well that one library really cannot substitute for another (though certainly can be layered with).