Doom Emacs

The most performance-wise optimized Emacs distribution.

Its abstraction is close to Spacemacs (and pretty much the same thing for an end user), in that Doom Emacs provides similar functionality through "modules" (instead of "layers"), which brings together packages and configurations for specific features, e.g. modules for programming languages as C, C++, Clojure, etc. Also, just as Spacemacs, it's possible to install packages individually and then tweak them as you like. However, instead of a single file (.spacemacs), Doom Emacs provides those configurations in 4 files for the user to edit: init (modules), packages (individual Emacs packages), config (to tweak your Emacs stuff), custom (miscellaneous).

Another major difference is that Doom Emacs is optimized for performance. So it's a lot faster than Spacemacs. On the other hand, Doom loses very much to Spacemacs in functionality, as it has way less modules than the latter has layers. Also, Doom is frustrating in comparison to Spacemacs because, just as advertised, some of the defaults (or should I say the maintener's twisted defaults) are too much opinionated and is not as sane, e.g. the latter has a way better and saner session management through "Layouts" than Doom has with "workspaces"; Doom use of popup.el is also frustrating for some buffers like the info buffer. So while you gain in performance, you lose in functionality.

Doom Emacs wins in having an active leader though, while Spacemacs is essentially in a state of Anarchy (good or bad, it's up to you). The community of Doom is more helpful: it's very active and supportive on Discord.

[Edited by Lunatica, December 05]