Is there functionality that I am missing within Visual Studio Data Tools (2015) that allows you to export the results of a data comparison? It looks like you can only export the DML script generated? Thanks!
The functionality was deprecated and hidden in Visual Studio 2015 and later. It wans't removed completely - you can still create a data comparison by creating a file with the .dcmp extension and adding it to your Database project. Once you open it, you'll be presented with the Data Comparison wizard.
Unfortunately, you can't save your table selections and options. The only things that can be saved in the file are the connection strings. This means that you'll always have to use the wizard to make a data comparison.
For example, one of my dcmp files looks like this :
<?xml version="1.0" encoding="utf-8"?>
<DataComparison>
<Version>10</Version>
<ConnectionProperties1>
<ConnectionString>Data Source=1.2.3.4;Initial Catalog=MyDb;Integrated Security=True;Persist Security Info=False;Pooling=False;MultipleActiveResultSets=False;Connect Timeout=60;Encrypt=False;TrustServerCertificate=True</ConnectionString>
<FullDisplayName>My Source Name</FullDisplayName>
</ConnectionProperties1>
<ConnectionProperties2>
<ConnectionString>Data Source=A.B.C.D;Initial Catalog=MyDB;Integrated Security=True;Persist Security Info=False;Pooling=False;MultipleActiveResultSets=False;Encrypt=False;TrustServerCertificate=True</ConnectionString>
<FullDisplayName>My Target Name</FullDisplayName>
</ConnectionProperties2>
<SessionSettings>Default</SessionSettings>
</DataComparison>
BTW, SSDT is now a separate download currently at version 17.3 for Visual Studio 2015, 15.4 Preview for VS 2017.