I hate the best editor debate because I think it's distracting from what's more important — what both editors can learn from each other and what both need to do to improve. I used Emacs for years, switched to Vim because of RSI, then recently switched back to emacs+evil. Frankly, for what I do most (R, R+knitr, C++ with clang autocomplete), no single editor is great. First, there's too little ability to switch between modes within a single buffer in both Vim and Emacs. The feature's entirely lacking in Vim AFAIK, and poly-mode in R uses a high level hack that (1) doesn't play well with other modes (including evil) and (2) has so thoroughly destroyed my documents in the past I refuse to use it now (mostly because it uses many buffers behind the scenes, which destroys undo history).

In general, if you want flawless R support in certain blocks of text (as in a .Rnw file) in between LaTeX blocks that are fully connected to AucTeX, well... you're out of luck. And Vim... Vim-R-Plugin is useful, but it's sort of a painful hack to use tmux just to get R and Vim to talk (and I'm saying this even though I love Tmux).

Vim has YouCompleteMe, which is smooth as silk compared to Emac's options (which are painful and poorly integrated, especially with clang). But some lower-level issue in Vim causes this constant error message in Vim whenever YouCompleteMe uses clang — bloody annoying. So overall, both editors have huge issues that would require serious overhauls or tedious bug fixing in various modes. Sure, Emacs does AucTeX better, but until it does everything better (or Vim does everything better) it's a flawed editor. Both are flawed editors. But sadly everyone thinks the best course of action is to start fresh — which usually creates a feature-poor flawed editor on a new shiny foundation, that fails to attract developers because it's feature poor. (apologies for ranting -- jetlag).