Most people tend to be in love with Gauges and Pie-Charts. They look nice, are colorful and create the perception of true executive dashboards. But many experts will agree that Pie Charts and Gauges are a poor visualization for KPI data and a poor visualization format for executive dashboards,
Why are they poor visualizations? Well, both of them lack the visualization of trends that Line charts do provide. They only give you insights in a single period. Think about it, unable to see trend information while the data is there is a big RED FLAG for a strategic dashboard. How can you take decisions with data based on a single period? How do you track improvements if you are looking at a single period?
There are a couple of good sources on the web when it comes to data visualization, here are some well known specialists: