Great story on Poynter on headline styles… here’s a snippet:
Type set in all capitals is harder to read. Whenascenders and descenders are eliminated, words become rectangles and are harder to recognize. This is particularly true for long lines of text.
THE ALL CAPS STYLE IS HARDER TO READ. WHEN ASCENDERS AND DESCENDERS ARE ELIMINATED, WORDS BECOME RECTANGLES AND ARE HARDER TO RECOGNIZE. THIS IS PARTICULARLY TRUE FOR LONG LINES OF TEXT SUCH AS THIS.
Reserve the all-caps style for small amounts of type — one- to three-word headlines, labels, headers, and other navigational items that only use a few words.
Sans Serif typefaces tend to work better in all-caps than serif faces. In this case, the serifs get in the way and erode readability and reading speed.
In addition, using all capitals takes up more space…