Both the software are used for Data Visualization. But according to experts, it is not right thing to compare the two tools. R is best used for exploratory analysis, while Tableau is better utilized for visual information in form of dashboards.
-R is difficult to learn compared to Tableau. To learn R, basic background and coding syntax is required such as how data is stored- vectors or matrix. Whereas Tableau is user friendly as is just a click away from getting the result.
-Tableau is limited in visualization whereas R is flexible for any types of visualization or even for most of the software platforms.
-R is an opensource tool. New packages and libraries released periodically with no cost which enhances the user ability to learn whereas Tableau can be costly for upgraded features.