People · 1989
One great advantage which poetry has over prose—one sense in which, we might even say, it is considerably more beautiful—is that it fills up space approximately three times as rapidly.
— James Thurber ‧ Collecting Himself: James Thurber on Writing and Writers, Humor and Himself

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Poetry wins this comparison because it fills a page faster. The joke starts with grand words about beauty, then judges writing by how much space it occupies. That sudden change in standards makes a practical concern sound like a great literary advantage.
Context reviewed