[CentOS] Postfix setup

I'm trying to clarify the various ways in which I could set up
Postfix + Dovecot + SpamAssassin under CentOS-7,
and I'd welcome any comments on the following remarks.

As far as I can see there are 3 standard ways of setting this up:
  1. Use amavisd
  2. Use dovecot + pigeonhole/sieve
  3. Use spamass-milter

At present I'm following (2), but am thinking of going over to (1),
since this seems simpler.
(Amavisd wasn't available when I set up CentOS-7, so I didn't consider it 
then.)

It seems to me that (2) is using dovecot in a slightly odd way,
since as far as I can see dovecot normally takes email from ~/Maildir/cur/
and then moves marked spam.

I'm not quite sure if (3) is a genuine alternative,
or if it is why it is not the standard since it seems very simple?

-- 
Timothy Murphy  
e-mail: gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin 2, Ireland