Background processes don't block the main thread, the extension points are better thought out and the development experience in working on extensions is a LOT better, js/coffee are better languages than vimL, and display is not limited to a fixed grid of text cells.

The downsides are that it's comparatively slow. The vim keybinding emulation isn't great but I can now use it without getting frustrated using ^[ to get back to normal mode.

I still use Vim for most things but I do Clojure/Clojurescript in Emacs evil-mode, and Typescript in Atom.