Venn Diagrams can emphasize Simple Relationships
The circles do well with simple relationships involving two or three populations. Sometimes four can work. Though words can usually make the same statement, the visual representation works on a different part of the brain. Sometimes, the simple logic of the diagram makes the difference; all the areas have meaning and they all seem present in a more concrete manner than with plain text.
Venn diagrams do well for explanation.
Data tables or charts should be used for specifications.