The compelling differentiator is that all the features are easily discoverable, you don't need to read a manual before you know how to save/quit/search/replace/use tabs/undo/redo/macros/etc.
For a considerable time in my professional life I was forced to use Windows. I would still have access to Linux VMs, in which I spent most of my time, using vim as the editor but whenever I wanted to take quick notes, sanitize text, stash away some info I need in work etc., I'd just use the notepad on Windows.
Then I found Notepad++. The UX is just so great (though I never figured out how to delete all the line ending spaces and it's sometimes nagging me).
So I love both Vim and Notepad++, different use cases. Different reasons.
I use vim and geany and code::blocks and np++ for different things at different times.
geany, codeblocks, and np++ are all scintilla, so what I am really saying is I use both "something like vim or emacs" AND scintilla, and there is no dichotomy.
And what is "something like vim or emacs"? The two are nothing like each other.
Anyone who used either vim or emacs already knows why they do so, and already knows that none of the reasons anyone will say they like any normal editor will apply. Everything anyone says will either be something vim or emacs already has their own answer for, or will be things they actively don't want.
Question seems somewhere between disingenuous to inexplicable. I would say rather than an actual request for information, it was just to say "I like vim or emacs", except "I like vim or emacs" makes no sense because they are not substitutions for each other.
Unless you're looking for a compelling reason to switch. For example, I use VS Code sometimes because of its markdown preview pane. That's not available in emacs or vim (to my knowledge).
emacs works great on windows. I'm not sure if there are things notepad++ does that emacs can't but I've never had any windows-specific issues with emacs.
It depends what your "serious" work is. I have used it to edit well over 300 million words of text, reformatting scripts to add tagging etc, large scripts of complex regex to data clean (although nothing I know of beats TextCrawler for that task), even writing code in several languages - though of course a proper ide is more useful for many coding tasks. VS Code for example absolutely chokes on large files. Sublime does an ok job - but not one I can rely on for larger batch jobs. NPP excels, and I can quickly do thousands of changes on thousands of large files quickly. NPP also has many plugins (like Sublime etc), and its utility depends on them as much as the other text editors do.