Hey Chief,
Your EXS can translate the Giga files into EXS format, so don't rule out VOTA. I have VOTA and Symphony of Voices (choral sounds junkie here) and they're very different. You can keyswitch vowel sounds in VOTA, but if you're looking for smooth/gentle evolving vowel sounds, Symphony of Voices has a few ah-ee-ohhh-type things. When you layer them, or use them in rounds, and add some of the phrases they've recorded, the result is beautiful. If you want to give a listen, I have a piece on my website that uses all Symphony of Voices samples; it's Audio Clip 5 here:
http://kerrymuzzey.com/audio-only.htmlOtherwise, search the forums on here because there have been a few threads about choral libraries. Happy hunting!
Kerry