Amieroh Abrahams builds some graphs:
In Excel it is challenging to eye-ball which changes have been made to a graph, especially if these were minor changes. With R (and some easy to use version control systems), you can see exactly which files were changed. Also, in Excel, a user would usually draw a graph on a single Excel document, and if the same graph is required on a different data set, it is common to copy-and-paste a bunch of manipulations and configurations to another document. Such repeated human interaction is prone to introducing errors, as well as consuming a large amount of time. With R we can avoid this by creating functions, which can be used to run the same code on different data sets simply by changing the input, thereby producing reliable outputs and saving us a lot of time.
Click through for the article. One big thing in Excel’s defense that I did not see here was that it’s a lot easier to perform specific story-telling in Excel visuals. For example, highlight just these two data points, or annotate this segment of the visual. You can do those things in ggplot2 but it’s considerably more difficult than “right-click the data point and format.”