Where 37Signals is:

• ERB for view templates
• MySQL for databases
• MiniTest for testing
• Fat Models, Skinny Controllers

And Prime is:

• Haml for view templates
• PostgreSQL for databases
• Rspec/Cucumber for testing
• Skinny models, controllers, and a service layer

Link: [Rails has Two Default Stacks

Steve Klabnik]1 via words.steveklabnik.com