Hi Maya,

To be fair to the pie, they're ok for 2 or 3 series that are significantly different in size since it'll be easy to compare the segments to see which is biggest etc.

However, if you have more than 3 series, or the series are close in size then a bar chart is by far the superior way to display this data, as they allow the reader to make an immediate, subconscious comparison requiring almost no effort. Particularly if you sort the bars in ascending/descending order.

Mynda