I've done both vanilla postfix, dovecot, rspamd, etc and mailcow.

For me the reason I use mailcow is it's a few commands and I have a fully functional mail, calendar, and contacts server with a web UI. It can then be updated with a single update.sh.

Using mailcow I don't need to mess around with virtual domains, connecting it to mysql, DKIM, etc which is far more than a few commands.

I also get a nice admin UI, web mail and CalDAV and CardDAV which you don't get with the above.

Also I'd consider the separate containers a good thing so that if rspamd, or clamav, for example, has a CVE they can't pivot to other parts of your mailserver.