[Zope] add content via ZMI or custom form?

Could someone discuss this point: when should I allow a user (say with a Writer-role) to add content to the site 1) via the ZMI, choosing Add DTML document and such like 2) via a custom made form, using submit (or upload) Is the main difference that for 1) one needs more HTML knowledge? Or are there other considerations as well? Kind regards, Roger