Imagine you are reading two reports.
Which report is better?
When making a report or presentation, you must account for style and substance in equal measure. A lack of style diminishes the potency of substance and vice-versa.
Style is concerned with presentation and design. Is the work presentable to the audience? Does the form fit its function? Is there a common theme that binds everything together?
Substance deals with relevance and content. Is the work insightful or informative? Does it accomplish what it's set out to do? Is the result useful to the end-user?