None. Vim is zippy as shit. Emacs stutters on files an order of magnitude smaller than it takes to slow down Vim. In no small part because my Emacs is bloated but I like my Vim minimalist, but still mainly just because Vim is faster than Emacs period, and not by a little.

I don’t mean no MT is a hard pass on Emacs for me obviously. But every time I pass up Emacs to use another editor it’s a performance issue which multithreading would take care of handily, even if it went no further than a separate thread for the UI.