Fair comparison
Universal Document vs HTML
HTML is a presentation and application substrate. UD defines document state, lineage and evidence semantics and can use HTML as a browser carrier.
Not a forced replacement
UD is designed to coexist with established formats. The practical question is which object should carry structure, state and lineage, and which formats should remain compatibility exports or required delivery formats.
Evaluate with one real workflow
Compare how each approach handles revision, finality, portability, machine readability, provenance and recipient friction.