About the FS1 music being choppy...it was build with midi synths, not sampled instruments and obviously optimized for the 11Khz range. It could have sounded better, but I guess the size was a problem. In 22 Khz the whole music section would have been twice as large. It was back in '98, right?
But I also think that the FS1 tracks were better than the FS2 stuff...not from the sound, but from the composition.
About the choirs in FS2...that ain't synth choirs! These samples come from the library "Symphony Of Voices", which contains recorded samples of some london choral choir, that consists of around 80 people (if I am not mistaken here). A synth choir would come from a synthesizer and that was not happening here!
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http://www.spectrasonics.net/symphonyvoices.html
BTW, I'm currently trying to score BlOps

(Blackwater Ops)
Have a nice day!