At what level do ammā baʿd and hādhā dhikr chiefly differ?

Final Chapter: Excellence of Opening, Barāʿat al-Istihlāl, Transition and Conclusion

• The former is an ending, the latter a metre
• The former is a conventional divider, the latter refers to preceding content
• Both are forms of paronomasia
• Both are names for a qaṣīdah