Sure. The XS Pre was more transparent and seemed to be extremely tonally neutral. The XP30 was slightly warmer and richer sounding. The XS was extremely dynamic, clean, and detailed sounding, especially micro dynamics while the XP30 was just slightly veiled.
Interestingly, I had this same friend's XP30 in my system and compared it to my XP20 for about a week. I preferred the XP30 because of its warmer/richer sound and it extracted a bit more detail than the XP20 does, however, after hearing the XS pre's neutral tonal balance, that reminded me more of my my system with the XP20.
With all of this in mind, I now lean slightly toward a more tonally neutral presentation. I loved the XS Pre in my friend's system, however, at more than twice the price of the XP30, there is the question of value. As one goes up the line, the more expensive units are clearly better, but diminishing returns definitely kick in.
I also directly compared the XA160.5 to the XA16.8 in this same friend's system and found the differences very similar to the XP30 vs the XS Pre. I wrote a fairly lengthy comparison on WBF and perhaps Audioshark which you could probably find by searching the Pass .8 threads.