Quando usar um Quadrant Chart
You want the chart to prompt an action
Prioritisation, triage, portfolio review. Naming the quadrants tells the reader what to do about each group, which a bare scatter plot never does.
Two measures genuinely define the decision
Impact against effort, growth against share, severity against likelihood. Both axes have to matter, or one sorted bar chart is the better chart.
The dividing lines have a real justification
A budget threshold, a target, the median. When the boundary means something, the quadrants mean something.
You have a manageable number of items
Enough points to see groupings, few enough that each can be labelled — roughly ten to fifty.