Values of CD are limited to 255 characters whereas CV are limited to 200;
Custom Dimensions are more efficient as they need less storage and reports can be generated faster;
Custom Dimensions are easier to track since only the Custom Dimension ID and Value need to be set in the tracker whereas, for Custom Variables, the Name, Scope, Index, and Value need to be set during tracking;
Custom Dimensions are easier to segment as the segment name will be the name of your Custom Dimension in the UI;
Each custom dimension has its own report while Custom vars have all one shared report.
What is the difference between Custom Dimensions and Custom Variables?
June 6, 2018
The features are pretty similar, but there are few main differences between them:
To find out more, take a look at our article about Differences between Custom Variables and Custom Dimensions.