Solution Navigator from the Visual Studio 2010 Productivity Power Tools first merged Solution Explorer and Class View. It added the ability to expand code files to navigate to its classes, expand classes to navigate to their members, and so on. In Visual Studio 2012 and Visual Studio 2012 this functionality became a standard part of Solution Explorer:
Still some people never use the Solution Explorer to navigate the code symbols and methods. In this case expansion arrows on code files only create distraction in the Solution Explorer window. There is no option to control the availability of file expansion, but there is the UseSolutionNavigatorGraphProvider dword registry value (discovered by Julien Lebosquain) that you can set to 0 to disable class view in Solution Explorer. The registry key for this value is HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0 for Visual Studio 2012 and HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\12.0 for Visual Studio 2013 correspondingly:
Now you can select the better view for yourself.