When comparing Emacs vs Yi, the Slant community recommends Emacs for most people. In the question“What are the best programming text editors?” Emacs is ranked 9th while Yi is ranked 44th. 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 Combines and improves upon the best text-editing features from your favorite editors
Yi has default configurations for Vim, Emacs, as well as CUA. It also makes several improvements that includes Sublime-like (multiple) cursors.
Pro More performant than Vim
Vim can be rather slow due the age of its code base. In particular, running large macros in Vim can be rather painful. Since Yi is being built from scratch it has been engineered for performance and with the benefit of hindsight.
Pro Extensible and modular editing features
As far as extensibility goes, Yi easily outstrips any other open-source text editor. Motions can be built from parser combinators, making them simultaneously flexible and modular - an open source hacker's dream.
Pro Plugins work together
Packages work together because they compile together.
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 Very few plugins available
Even though Yi is a general purpose text editor similar to Vim and Emacs, almost all of the plugins that have been written for Yi so far focus on supporting Haskell as a programming environment.
Con No way to reuse your existing customizations and keybindings
If you have spent years crafting your .vimrc or .emacs, there's no way to reuse it in Yi. You have to start from scratch.
Con Requires Haskell to compile and configure
GHC + Haskell packages makes for a rather large installation, which is a big ask for a relatively obscure terminal editor.