I'm not sure there is such a big divide: emacs is the OS in a way (in the same way a browser is one these days) and the tools are all the extensions (including

I'm not sure there is such a big divide: emacs is the OS in a way (in the same way a browser is one these days) and the tools are all the extensions (including those built in). The union of all extensions is more than the sum of all the parts. The difference is that the interface between tools in emacs is usually much richer than in UNIX (for example a buffer is a more complex abstraction than a file).