I could notice the slowness of Atom when I compared it to VS Code. Sublime is also noticeably faster than VS Code, but the gap doesn’t feel so wide that I want to jump the ship.
I think it depends on the number of characters in the file that make the difference more noticeable.
I guess it’s things like AWS Elasticahe that made them want to provide their own service without sharing the code with their soon to be competitors.