Spacemacs vs Intellij IDEA

Spacemacs combines the Emacs platform (with the full power of the Emacs plugin ecosystem) and the Vi keybindings (via EViL), all in the same box.

At the heart of Spacemacs, the configuration layers group packages configuration into semantic units that can be toggled on and off. The architecture is simple but powerful, allowing the user to easily manage configuration dependencies between hundreds of packages.

Spacemacs is the biggest community-driven Emacs starter-kit.

Documentation is mandatory for each new configuration layer and can be accessed directly within the editor in Org format.

Emacs runs on Gnu/Linux, Mac OS X, and Windows.

Stuff like version control, file management, good default theme are all configured out of the box.

Space-lead key bindings are organized in mnemonic namespaces. For instance, buffer actions are under SPC b, file actions are under SPC f, project actions are under SPC p, search actions are under SPC s, and so on. Keybindings are consistent across the whole distribution thanks to a set of conventions.

There's no need to reach for the mouse again since Spacemacs can be fully controlled with keyboard.

Evil package is a first class citizen and Spacemacs embraces it from day one. Evil package allows Vim users to be productive very quickly while still allowing regular Emacs users to use Spacemacs.

Files can be edited in Spacemacs remotely.

Allows for great organization applications that can be saved in future-proof format, plain text, can be integrated with org, LaTeX, markdown, HTML, Literate Programming and be committed to source control.

Spacemacs has some great features for taking notes, tracking to-do lists, and tracking time.

LaTeX allows for auto-completion, syncing, and more.

Has great daemon support, which can mitigate the issue of slow startup.

Sometimes you only have terminal access, over ssh or something.

Syntax highlighting and org-babel extensions.

The community surrounding Spacemacs is very active and there is a welcoming gitter chat for users to ask questions.

Spacemacs got its name from the fact that it is uses the space bar as a default leader key. The key was chosen because it is easy to press and to hopefully lower the risk of RSI.

New functionalities and fixes are added to Spacemacs every day, while release cycles are short.

Elixir layer which uses the Alchemist package is the best way to edit Elixir code out there.

There is a free community edition (open source) and an ultimate edition, which you can compare here.

The ultimate edition is available for free for one year for students but must be registered through an .edu e-mail account.

Uses a fast indexing technique to provide contextual hints (auto-completion, available object members, import suggestions).
On-the-fly code analysis to detect errors and propose refactorization.

IDEA has a clean, intuitive interface with some customization available (such as the Darcula theme).

IntelliJ IDEA hardly ever crashes or has any issues that plague other Java IDEs like file corruption or slowness.

IntelliJ supports many languages besides Java, some of these are: golang, Scala, Clojure, Groovy, Bash, etc...

IDEA places an emphasis in safe refactoring, offering a variety of features to make this possible for a variety of languages.
These features include safe delete, type migration and replacing method code duplicates.

Many plugins are available for almost any task a developer may need to cover. Plugins are developed by Jetbrains themselves or by 3rd parties through the SDK available for writing them.

A very complete development environment support.

The documentation is exhaustive, easy to navigate, and clearly worded.

With ability to step into a certain part of a large method invocation (Shift+F7), drop frame, executing code snippets, showing method return values, etc.

These simplify the daily work, e.g. copy/cut a whole line without the need to select it.