Benefits of Writing a Sentence Outline.

1. Clarity. 
   If you can't write a clear sentence summarizing the paragraph's point, you certainly can't write a clear paragraph.
    
   
2. Flow of argument. 
   It is much easier to quickly judge whether the present order of paragraphs (as sentences in the outline) makes the most effective argument.
    
   Omitting one or more paragraphs might still make your argument.
    
   
3. Efficiency. 
   Revision of the plan of paper is much easier and quicker if you have only to delete and re-order sentences.
    
   Doing this on the completed draft involves much more work.
   1. Since a concept must be explained when it first appears, interchanging paragraphs will require moving definitions.
   2. Paragraphs should flow smoothly into each other. Reordering paragraphs may require extensive rewriting.
       
      
4. Writing to length. 
   With a sentence outline you can easily judge the manuscript's length and modify it to keep the essential material within the desired length.
    
   
5. Time. 
   All the above -- clarity, argument flow, efficiency, length management -- can be done faster using a sentence outline.