Presentation on the usage of bar charts in comparison with pie charts is available on Alchemer web page. Bar charts are recommended to show trends and comparisons; pie charts are recommended when we compare values to a certain entirety.
In principle, it is advised against the use of pie charts when we want to show the precise value, or when we want to compare different values. It is also recommended to limit a pie chart to only a few categories. Bar charts, on the other hand, can serve as a good way to show comparisons between categories.
In general, it can be detected that the trends are reluctant to use pie charts because the human eye can’t detect the exact degree of angle at which we display the value of categories in pie charts.