Just adding to this thread:
I’ve dispensed with Symphonic Choirs, simply because of stability problems with the VST, and the fact that Word builder didn’t work.
The little Pipa VST listed above also caused crashes in Dorico on Quit.
Anything that’s just doing “Aaahs” is only going to give the impression of a voice, in the same way that an Impressionist does an exaggeration or ‘essence’ of Shatner, rather than a facsimile. Anything else is just going to require lots of work, and still sound a bit artificial. But I’m actually OK with an “Impression”.
SoundIron’s Requiem Lite voices would be good if they weren’t so dreadfully flat - and that goes for the Olympus voices, too.
Noteperformer is surprisingly good for parts songs and motets, but ironically it’s poorly balanced as a choir against NP’s instruments. (Also, no way to turn down the vibrato, as with many singers.)
In the end, I’ve actully created my own “choral instrument” by layering the Garritan GPO5 choir voices together with some of the Logic Pro choir samples, as ‘an instrument’ in ARIA Player.
It particularly works well as a solo or choir against an orchestra.
The real problem is that you want different levels of articulation on different notes - repeated notes and short notes need more accent than other notes in a legato phrase. The wrong level of articulation in the wrong place is what makes it sound artificial. I guess I could try crossfading to other vowels just to mix it up a bit…