I use many text editors everyday to perform tasks. Here's my list.
Notes is the easiest to use and most convenient of my text editors. I like that it keeps all of my notes in its collection style interface and they are all viewable and edible on my Mac, iPad, and iPhone.
I use Notes mostly for documents I think will want to exist for a long time.
Because Notes generally uses a proportional font and does the transitions to friendly characters, for instance straight quotes to curly quotes, I don't tend to use it to write about code or anything that uses spaces for layout.
I used to use TextEdit where I now use notes. But the whole iCloud thing moved me to notes. Now I use TextEdit not for saved documents, but when I need a nice little text editing window on my desktop. This can either be use for goals and ideas related to my current work or as a cut and paste clipboard.
I have the Preferences for TextEdit configured so that it won't make many corrections to my content, such as changing straight quotes to curly quotes.
I write code all day and work in Terminal. People who do this usually have some command line editor that they know how to use. I use Vim. The documents I most edit with Vim are version files and Git commit messages.
Xcode is what I used to edit Swift, Objective-C and other app files. It's not the best editor, but it has features beyond code editing that make it work very well for the task. It does get mildly better with each yearly version.