I recently purchased VSL Special Edition Vol.1 and I felt like comparing it to the other sounds I already owned. After discovering that VSL comes with a Sibelius playback sound set, I jumped into Sibelius quicker than my dog jumps into my dam when no one is looking (which is very quickly, obviously). I made a very quick score (so, not my magnum opus guys) and played it back with different devices for some afternoon fun (my idea of fun is a little skewed from the norm).
I recorded my screen and uploaded the huge file to YouTube from my rural ADSL2+ internet speed (*cries*), so take the time to enjoy it!
It is probably not the best representation of each playback device, so here is the little note.
VSL: The special edition only has 2 velocity layers, which means extreme dynamics and everything in between is faked. The higher end libraries by VSL has a lot more detail, dynamic layers and are generally a lot more kickass when it comes to realism. Check out the actual demos from the website to hear demos people actually put many hours into crafting (there is even a great demo of the Rite of Spring using the full version of VSL).
NotePerformer: It combined synthesis with samples and actually competes well with sample libraries. It does sound like it lacks some clarity compared to EWQLSO though (probably not evident in the YouTube video).
Sibelius Sounds: It was designed to work with Sibelius so it follows the score well with dynamics and articulation.
EWQLSO: It actually does not play back the crescendo/decrescendo hairpins at all because the library is velocity based. There are some patches that use the mod wheel to crossfade between the dynamic layers, although, the library is very dated and does not have sampled legato transitions that modern sample libraries boast.