SPCAF Professional is targeted to individual developers/architect who want to analyze locally eg. in Visual Studio or the standalone client application.
SPCAF Build focusses on teams who want to integrate SPCAF in the continuous integration process, eg. Team Foundation Server, Visual Studio Team Services (previously Visual Studio Online), Jenkins, Atlassian Bamboo or TeamCity.
The results and reports of both licenses are identical.
More details can be found on the Feature Comparison Chart.