When comparing ApexSQL Data modeling vs Schemaball, the Slant community recommends Schemaball for most people. In the question“What are the best relational database design and modelling tools?” Schemaball is ranked 13th while ApexSQL Data modeling is ranked 19th. The most important reason people chose Schemaball is:
Schemaball can read schemas from multiple sources such as SQL schema dumps, flat files or live databases.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Source control support
(planned) support for: Git, Mercurial, Perforce, Subversion, and Azure DevOps Server (TFS)
Pro Supports reading schemas from multiple sources
Schemaball can read schemas from multiple sources such as SQL schema dumps, flat files or live databases.

Pro Interesting twist on visual interface
Gives a quick way to grasp an overview on the past/present complexity of the database (or group of tables) undergoing inspection.
Cons
Con Only SQL Server
But MySQL support is planned.
Con Visualizations may be hard to get used to
Since schemas are visualized by using stylized "schema balls" it may be hard getting used to them since they are so different from the other, more straightforward options.
