SQL Server / SQL Azure Schema Compare

Need more reputation to comment, sorry for redundant answer: this window can not be found in VS options. Start comparison and click options button

The only way I've been able to do this is to import the SQL 2012 DB to a database project targetting SQL Azure, then compare the project to the SQL Azure database.

There actually is a non-cumbersome method to overcome this problem. Just open up the schema compare options and make sure the "Allow incompatible platform" box is checked