Boys and Girls,
What you are missing from this "discussion" is that we don't necessarily write for real the same as we write for the samples.
When i am creating with the library, to be played by the library, I have the luxury of manipulating what I am writing at any given moment to make it sound as good (and feel as good) as I want it to be -- and sometimes that means we write things that we may not have done for the "real guys". And sometimes, it's MUCH harder to write for the samples -- since they are unforgiving.
I mean -- with a good room of musicians, you can give them just about anything, and the best players will make most anything sound as good as it's going to sound. The samples are not nearly as accommodating. If the writing stinks, the sample lib will make sure everyone knows.
Conversely, simply taking an orchestration and trying to render it with the lib is not always going to get results -- since a good orchestrator has the luxury of knowing that the musicians will make it right. But the samples only can do what they can do... and if the orchestration is not written specifically for the samples, you may or may not get the results you wanted.
Yes, I do this for a living. And my work can be heard internationally. And I can't tell you which tracks are real and which are fake (I get to conduct full orchs as well as doing the fake work) else my clients will shoot me. There's a new album coming out in about 8 weeks for a major artist in the US, for a major label, and this label is known for paying for big orchestra dates... except on this project - and the head of A&R for the label (who is a respected conductor) wrote me a note, congratulating me, and wanting to strangle me at the same time -- since he knows what I just did.
The point is that there are some guys doing some very high level work -- and it usually involves some serious audio engineering and producing skills to go with the musicianship. The samples alone only get you so far -- then you have to make them sound and feel real.
Can I fool the listener? You betcha. It may be a hybrid -- sometimes using a soloist + section samples. But i can fool the listeners. Even if the listeners are musicians and conductors. If I can do it, so can others. But remember, we're probably writing for the samples, not the real guys. It's not nearly as easy to do well as some represent. And then add decades of audio and conducting and playing experience -- yes, there are some guys pulling it off. And I'll guarantee that many of us have signed non-disclosures, so we can't really tell you which projects are fake.
And are we trying to sound "real" or are we trying to sound organic and emotional? What's the PURPOSE of the music?
If you want to be real good at this, go conduct and play in real orchestras for about 20 years, then come back to the samples.