[Exim] maildir Vs. mbox

Okay, default for (x)NIX is to store email in a bindir mbox (ie,
/var/mail/username). I have changed to a double hashed spool bindir (ie,
/var/mail/u/s/username) because of disk IO issues, and it helped ALOT!
Now, I am setting up RAID 5, and want to make the system run as
efficiently as possible with the type of hardware I have, for 50,000
users. Very few users are using imap to check mail.

Reading what somebody said on this list, it is easier on the system to
store each message in a seperate file (maildir), because it doesn't have
to be moving files around to temporary files, or eating up memory to open
them. However, I was reading the pine notes in the pine distribution, and
it said that mbox was better, because it doesn't have a bunch of files to
thrash around.

???????

Does anybody have a clue which is better? Seems to be a religious issue
with programmers. Which is better for exim and pop3 combination? mbox
format in a home directory, or maildir format? Granted that maildir won't
work with pine, but I am not concerned with that at the moment. Pine can
check pop3 anyway.

Sincerely,

Richard G. Duvall