When should you use PloneFormGen, and when should you develop a custom content type and use Plone's built-in edit form generation? They each have their pros and cons.
Use PloneFormGen when...
Frequent additions or revisions of forms are required. Those needing the forms will appreciate not having to wait for development resources, and your developers will be spared the interruption. Also, you won't have to orchestrate a restart of Zope for changes to take effect.
Data will be collected and socked away somewhere, without being called up and edited through the Web later. As seen under Saving Submissions in the ZODB, PloneFormGen doesn't provide much of a viewing or editing interface for saved data.
Use an honest-to-goodness Archetypes content type when...
The collected information must be processed, reorganized, searched, or made available to other users while it's stored on your site—it's not just making a one-way trip into a copy of Excel at someone...