The fact that XLIFF might be better for someone then PO (explained on the link you posted up here), does not mean it is better for us. Someone who knows both need to do a comparision. Show us the needs in Drupal which XLIFF fulfills, and are not possible with PO files.
I don't actually know anything about either translation process, however I did come across this link in my research about what PO and XLIFF are and there are quite a few pros/cons laid out here, as well as use cases from someone at Sun and Novell:
http://mail.gnome.org/archives/gnome-i18n/2003-October/msg00022.html
Angie, unfortunately the questions put up in this beginning of the thread are not relevant to us. We are not using the binary counterparts of PO (MO) at all, we have no interest in the capabilities of the library provided (ie. memory consumption, etc., as we are not going to use that Java lib :), and thus we know how partial translations, etc. are handled in our implementation :) Goba