I know this isn't what you're responding to, but... I do notice the difference between vim (or neovim) and spacemacs -- spacemacs is noticeably slower. I do still use spacemacs more than vim now, though, because its Clojure integration is better.
(aside-rant: evil-mode is also not really a substitute for vim -- when you say you're a vim user, people often ask "why not just use the vim emulation in editor-X?" and the reason is because vim emulation has never, in my experience, been as good an experience as vim, things always work subtly differently)
Having used vi for 25 years and vim for 20 years, I'm going to say that evil-mode is the first vim-emulation editor mode that was close enough for me.
I think there were two or three things that weren't right for me out-of-the-box, but 15 minutes and 30 lines of elisp later it was fixed. I really need to maintain a fork or something that is as much like vim as possible, but with options for enabling specific emacs features, because everyone has some things that emacs does that they like better than how vim does it.
My personal example: s/foo/bar/g on a line containing "foo Foo" becomes "bar Bar" by default in emacs, which I find to be amazing, but is definitely not how vim works.
Yeah, its minor differences, but they add up. Maybe its time I learned a little elisp and fixed it for myself, I really like spacemacs aside from the (minor) annoyances caused by not being vim.
(aside-rant: evil-mode is also not really a substitute for vim -- when you say you're a vim user, people often ask "why not just use the vim emulation in editor-X?" and the reason is because vim emulation has never, in my experience, been as good an experience as vim, things always work subtly differently)