Emacs will sometimes become slower (especially remote emacs), but it will always buffer your keypresses and do them in the correct order.
Jupyter (for whatever reason), doesn't do this with the result that I ended up wanting to create a new code block, but that keypress got lost and then i end up ruining my original code block.
I 100% noticed the difference, and it was super frustrating (fortunately I left that job, and have managed to avoid Jupyter in the new gig).
Emacs/Spacemacs can still be weirdly slow sometimes but UI responsiveness is generally miles ahead of all Electron-based software still.
Which makes it even funnier. Emacs is decades old and still uses quite a few ancient techniques that are only hampering it. Even with that, it's still so much better in terms of speed! Funny.
I think it’s only noticeable if you’ve used a native application for a while. It’s not enough to go from VSC to Sublime and back to VSC again for five minutes. Make an effort to use a native app for a week or a month and then switch back.