Obsidian (or Roam, Logseq, or Athens) feels like a different vehicle for information, it's useful when notetaking something that needs more structure (like a class).
nvAlt (and Simplenote) has felt better for faster scribbles or notes that are technical cheatsheets and such.
I don’t know. I used nvAlt daily for many years, then Ulysses, then Obsidian as of a few weeks go. They feel very similar to me.
They are all “very fast text editors that store your notes in a folder of text files and search them instantly.” I don’t think that the category needs a more specific definition than that.
nvAlt (and Simplenote) has felt better for faster scribbles or notes that are technical cheatsheets and such.