This perhaps used to be true if evil-mode was around in the 90s. I've used to use vim and eventually made the switch to emacs about 10 years ago, initially using viper and then becoming an early adopter of evil-mode - and it never felt less snappy than native vim, except for rare occasions when executing complex macros to do things that can't be achieved using regular expression. And the new native compilation makes any perceivable performance difference even more unlikely.