A pie chart is called a pie chart because it looks like a piece of pie cut into sections... It ISN'T called a cake chart, because a cake chart would be to controversial. - iow (in other words) - a...
They're both equally valid ways of displaying data. However - a pie chart is a better option when you need to show the relationship of each part of the data to 100%
There is no single answer to this question. It depends on what you are trying to do. Both types of charts are designed to interpret data. Pie charts are best is you want to show how each data element...