When comparing Emacs vs Ninja IDE, the Slant community recommends Emacs for most people. In the question“What are the best free IDEs for Python?” Emacs is ranked 7th while Ninja IDE is ranked 17th. The most important reason people chose Emacs is:
Emacs can be controlled entirely with the keyboard.
Specs
Question Ranking
Pros
Pro Keyboard-focused, mouse-free editing
Emacs can be controlled entirely with the keyboard.
Pro Total customizability
Customizations can be made to a wide range of Emacs' functions through a Lisp dialect (Emacs Lisp). A robust list of existing Lisp extensions include the practical (git integration, syntax highlighting, etc) to the utilitarian (calculators, calendars) to the sublime (chess, Eliza).
Pro It's also an IDE
You can debug, compile, manage files, integrate with version control systems, etc. All through the various plugins that can be installed.
Pro Works in terminal or as a GUI application
You can use Emacs' command line interface or graphical user interface.
Pro Self documenting
Emacs has extensive help support built-in as well as a tutorial accessed with C-h t.
Pro Free
Licensed under GNU GPL.
Pro Great documentation
With 30+ years of use the Emacs documentation is very thorough. There are also a lot of tutorials and guides written by third parties.
Pro Mini buffer
You can pass complicated arguments in the mini buffer.
Pro Ubiquity
Fully compliant GNU-emacs is available on many platforms, and they all understand .emacs configuration files.
Pro Rectangular cut and paste
Emacs can select rectangularly.
Pro Lisp customizations
With lisp customization, any behavior of Emacs can be changed. Update with pre-release patch can be also applied without recompiling the whole Emacs.
Pro Vi keybindings through Evil mode
Evil mode emulates vim behaviors within Emacs. It enables Vi users to move inside the Emacs universe.
Pro Visual selection and text objects with Evil
Evil is an extensible vi layer for Emacs. It provides Vim features like Visual selection and text objects.
Pro Support multi-line editing, multiple frame, powerful paren, crazy jumping style
Review the "Emacs Rocks" video.
Pro Provides org-mode
Advanced planning and publication which can start as a simple list.
Pro Has been widely used for a long time
Pro dabbrev-expand (Alt-/)
Dynamic word completion.
Pro Cross-platform
Works on Linux, Windows, Macintosh, BSD, and others.
Pro Enormous range of functionalities (way beyond simple "text editing")
Through its programmability, a very broad range of functionalities can be integrated in emacs, turning it even into a "single point of contact" with the underlying operating system.
Pro Integrates planning in your development process
You can jump straight from your org-mode files to programming tasks - and back - and build a seamless workflow.
Pro Helm plugin adds even more power to Emacs
Powerful commands, search, and more with the Helm plugin.
Pro GTK+ widgets support
Since version 25 you can run GTK widgets inside Emacs buffers. One of these is the WebKitGTK+, which allows the user to run a full-featured web browser inside Emacs with JavaScript and CSS support among other things.
Pro Syntax highlighting
Pro Extensible
Plugins can easily be created to add features that you may need but are otherwise missing from the IDE.
Pro Virtualenv support
Has out of the box support for virtualenv, which can be added when first starting a project or later through the settings.
Pro Embedded Python console
Has an embedded python console built in.
Pro Script runner
It is possible to run the project or any file opened in the editor with just one click.
Pro Find in files / find usages
Allows you to search one or more words, a regular expression, etc.
Pro Breakpoints
Pro Multi-platform
- GNU/Linux
- OS X
- Windows
Pro Built-in static analysis
NInja IDE highlights both static and PEP8 errors in a file. With each type of error having its own icon.
Pro Web-inspector
Pro Render HTML files
Also supports rendering HTML files currently loaded in the editor.
Pro Project management
Allows you to manage projects, saving descriptions and information about them and letting the user to perform file management related task inside the IDE itself.
Pro Easily locate code
Code locator allows quick and direct access to any file, function or class inside one of the project by simply pressing a few keys. Pressing Ctrl + K open a popup over a text field, where you can type the name of what you want.
Pro Symbols explorer built in
You can easily see all functions, classes and attributes in the current program.
Pro Written in Python
Pro Bash support
Pro Sublime snippets
Pro Multi-language support
Cons
Con Learning curve is long
While it's better than it used to be, with most functions being possible through the menu, Emacs is still quite a bit different from your standard editor. You'll need to learn new keyboard shortcuts.
Con Sometimes the extensibility can distract you from your actual work
If I ever want to lose half a day, I'll start by tweaking my .spacemacs config file.
Con Chorded keyboard combinations can be baffling
For example, for navigation it uses the b, n, p, l keys. Which for some people may seem strange. But don't worry, you can change it.
Con A lot of jokes in this serious software
Con Using Emacs on a new machine without your .emacs file
Con Latest version (2.3) is from 2013
But it looks like the project is still maintained towards 3.0 release.
Con Bad performance
Freezes and slows down often.