One BIG problem with EW Symphonic Choirs is that the ranges are wrong for standard choral literature. The Sopranos, for example, start on A above middle C (just think how much choral literature is impossible as a result) and goes above high C (two ledger lines above the treble staff). It's kind of like having a violin sample library that omits the G string.
Similarly, Bass section only goes as high as A below middle C, and then way down to "Russian Bass" territory.
There's a lot of unhappy EWSC users as a result, but the EW people keep sort of ignoring them on the forum. I guess there's no way to fix it at this point, so they just want the problem to go away. But it's a bit of a problem.
No one's sure why the libraries were recorded with these ranges. The most reasonable theory is that the developers took advice from the wrong people, i.e., Hollywood film-scoring composers who want the big "Lord of the Rings" sound, as opposed to actual choral conductors and composers, who could easily have told them what the real ranges are.
Yes, a VSL choir would be great. I actually LIKE the SC samples because of their relative lack of vibrato. On the other hand, what would be great is a library (maybe VSL could make it) that would have the choir recorded dry, with no ambience (SC has "room sound").