I loved Yasunori Mitsuda in Xenosaga, so I was disappointed to hear of his replacement for XSII and XSIII. However, Yuki Kajiura did a fantastic job with it and I find her sound fit the game a lot better than Mitsuda's. I have been listening to a Xenogears, Xenogears CREID, Xenosaga I, II, and III mix on my computer (while I read), and I have found that a lot of the times I a song captures my ear it belongs to Xenosaga I or II.
As for PriZm's work: Great work. I love pretty much anythings with choral female vocals, and this delivers well. It's almost haunting in the beginning, and mid song provides a nice contrast to the beat of the song. Good listen.