PGP/MIME vs S/MIME questions

Hello,

I'm a crypto newbie and I'm writing an application that needs to send
and archive signed and/or encrypted mail.  I've been looking over the
RFCs for S/MIME and PGP/MIME subtypes.  I've only have experience
sending and received messages using the pgp standard, and I'm unsure
as to what the advantages/disadvantages are of the two formats.

What I have guessed so far based upon my rather incomplete review of
the available data:

      - The pgp-based mime message types are the most used
        currently. But S/MIME is used in many commercial
        applications???

      - pgp-based mime currently relies upon calling either pgp or gpg
        (I haven't found free, in-process libraries to do the job)

      - S/MIME looks more complicated

      - S/MIME might be the standard for the future ???

Seeing that M2Crypto has a HOWTO for generating S/MIME messages, I was
hoping that there might be active developers using S/MIME or the
PGP/MIME-subtypes who might share their wisdom on how to decide which
to use.


Thanks in advance,

  -chris


-------------------------------------
References:

Status of two protocols   http://www.imc.org/smime-pgpmime.html
                          Includes table comparing algorithms for both
                          protocols (and see http://www.imc.org for
                          RFCs)

PGP/MIME:

  [1] RFCs 1847 and 2015

S/MIME:

  [2] http://www.rsasecurity.com/standards/smime/faq.html

  [3] RFCs 2630,2633,2632,2631 format, handling certificates, CMS,
      etc.