cron module idempotence when starting to use Ansible with an existing non-empty crontab

If you can template the crontab from a file, I would almost always do
it that way.

If you can use cron.daily or cron.weekly, I would almost always do it
that way too

Crontab module is for when you need to add very specific things with
Ansible, but it can't (and intentionally won't) perform surgery on
settings added by other users
without that prefix.

If you can ever manage entirely centrally, I would recommend doing it
(template /etc/crontab or cron.daily, etc)