> I had the impression VSCode had the technical superior plugin system

From my very limited exposure to VSCode's plugins, it seems they are a lot more limited in how they can change the editor's behavior compared to elisp code in Emacs[1]; if Atom plugins are similarly flexible, then I'm not sure you can say it's (strictly) technically superior if you can only implement a small subset of what you can do in competitor's system. At most it's better at some tasks and worse at others if this is the case.

[1] I didn't say "Emacs plugins" since there is no distinction between user-written elisp code and core editor elisp code and you don't need to create any plugin project or such, which I think makes for a much more organic and pleasant customization experience.