What's better: Raid 0 or disk for seperate pg_xlog

From rom http://www.powerpostgresql.com/PerfList/

"even in a two-disk server, you can put the transaction log onto the
operating system disk and reap some benefits."

Context: I have a two disk server that is about to become dedicated to
postgresql (it's a sun v40z running gentoo linux).

What's "theoretically better"?

1) OS and pg_xlog on one disk, rest of postgresql on the other? (if I
   understand the above correctly)
2) Everything striped Raid 0?
3) <some answer from someone smarter than me>

TIA,
--
Karim Nassar
Department of Computer Science
Box 15600, College of Engineering and Natural Sciences
Northern Arizona University,  Flagstaff, Arizona 86011
Office: (928) 523-5868 -=- Mobile: (928) 699-9221