The best thing to do might to test both in your envionment.
Perhaps you could install Bonnie and test both types of file systems.

I would reccomend that every filesystem get its own log - INLINE or
external.
For filesystems that you think will get a lot of IO, use an external
log.

I have been using dedicated JFS logs for every major filesystem that I
think will have a lot of IO.

If you're concerned, then just use a dedicate JFS log. It only takes
one PP.

FYI:

root@unxp1:/home>mount
node mounted mounted over vfs date
options
-------- --------------- --------------- ------ ------------
---------------
/dev/hd4 / jfs2 Mar 28 11:06
rw,log=/dev/hd8
/dev/hd2 /usr jfs2 Mar 28 11:06
rw,log=/dev/hd8
/dev/hd9var /var jfs2 Mar 28 11:06
rw,log=/dev/hd8
/dev/hd3 /tmp jfs2 Mar 28 11:06
rw,log=/dev/hd8
/dev/hd1 /home jfs2 Mar 28 11:06
rw,log=/dev/hd8
/proc /proc procfs Mar 28 11:06 rw
/dev/hd10opt /opt jfs2 Mar 28 11:06
rw,log=/dev/hd8
/dev/sybase_lv /home/sybase jfs2 Mar 28 11:06
rw,log=INLINE
/dev/Ptempdb_dat_lv /home/Ptempdb_DAT jfs2 Mar 28 11:06
rw,log=/dev/Ptempdb_dat_log
/dev/Ptempdb_log_lv /home/Ptempdb_LOG jfs2 Mar 28 11:06
rw,log=/dev/Ptempdb_log_log
/dev/Pworkdb_dat_lv /home/Pworkdb_DAT jfs2 Mar 28 11:06
rw,log=/dev/Pworkdb_dat_log
/dev/Pworkdb_log_lv /home/Pworkdb_LOG jfs2 Mar 28 11:06
rw,log=/dev/Pworkdb_log_log
/dev/Dtempdb_lv /home/Dtempdb jfs2 Mar 28 11:06
rw,log=/dev/Dtempdb_log
/dev/Dworkdb_lv /home/Dworkdb jfs2 Mar 28 11:06
rw,log=/dev/Dworkdb_log


Miles