This Compare Projects service is available since Sonar 3.4.
This service provides a way to compare different versions of a project or different projects. To access it, click on the Compare item from the left menu:
This Compare service is also accessible at project level. In this case, the service is initialized with the 5 latest versions of the project.
The list of projects/versions to compare is selected through the Add project drop-down list.
The list of measures to display is selected through the Add metric drop-down list.