I use both Emacs and vim on a daily basis. Emacs is my main editor and vim is for quickly dropping in to make a change in a terminal either locally or on a server. Both are amazing. Both are rock solid. Both are infinitely extensible. Both are free as in beer and as in freedom. I'm not afraid of paying good money for software. I don't think it is necessary to pay for a closed-source text editor when such good open-so…
Have you actually tried Sublime? It has split windows. And you can extend is pretty easily using packages. I've read many posts of vi and Emacs hardcore users who actually liked Sublime.
My browser and my text editor definitely need to be open source. Additionally, Emacs is really amazing, and like many others, I've been building this init.el for years (in my case months), meaning Emacs and I are really made for each other right now.