Emacs vs. CotEditor vs. Neovim

GNU Emacs is an extensible, customizable text editor—and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing.

CotEditor is a lightweight plain-text editor for OS X.

Neovim is a project that seeks to aggressively refactor Vim in order to: simplify maintenance and encourage contributions, split the work between multiple developers, enable the implementation of new/modern user interfaces without any modifications to the core source, and improve extensibility with a new plugin architecture.