Starting over feels clean, but it can throw away the most valuable part of a draft: the thinking you did while getting it wrong.
A rewrite is usually the right move when the draft contains the right material but makes the reader work too hard to find it.
Rewrite when the idea is there
The main point is sound but buried in the middle.
The sentences are longer than the idea requires.
The tone is wrong for the relationship or situation.
The draft repeats itself because the structure is not yet visible.
You have useful details, examples, or evidence worth keeping.
Start over when the brief has changed
A new draft makes sense when the audience is different, the decision has changed, or the central claim no longer holds. Save the old version; it may still contain research, language, or questions that belong in the next one.
Use a smaller intervention first
Try the least destructive edit that could solve the problem: clarify the opening, remove repetition, reorder two paragraphs, or shorten the ending.
A rough draft is not a failed final draft. It is evidence about what the final draft needs.