related to: Magnitude, Visual Encoding, Bar chart, Pie chart
For comparing the size of individual values – a magnitude comparison – columns or bars on a uniform baseline, are generally more effective than pie charts, particularly when there are small variations in the values of each element.
Smith, Alan. How Charts Work (p. 213). Pearson Education. Kindle Edition.
But why pie charts are difficult? > Because of their complex visual encoding.
More complex shapes can present problems in data visualisation context