Since a couple years ago you don't even need to open QuickTime for a screen recording, just ⇧⌘5 to bring up the system native screen recording tool. If you just want a quick screen recording and nothing more, it's a lot more convenient than OBS, especially if you want to record a window or part of the screen. In OBS you need to manually configure output dimensions and cropping is difficult and unintuitive, you can't just drag out a rectangle on your screen. I don't know what gp was comparing to when they said "an extremely good screen recorder for macOS with much less UI jank"; the native screen recording tool certainly doesn't have any UI jank and is lot more user friendly.

Where OBS shines are

- Precise control over encoding parameters;

- Mix and match multiple input sources, beyond just screen + system sound + mic; this includes rearranging and cropping multiple application windows;

- Add text, images, filters, etc.

In short, it has a lot more power user features. If you just want to quickly record the entire screen / an application window / part of the screen, native screen recording tool beats it handily.

I haven't used QuickTime, but OBS does allow you to record multiple things and overlay them in any way that you please. Which is why streamers typically like it. The "share window + camera overlay" is common, but you can also add templates, multiple video streams, etc. Can you do this in QuickTime? I know most basic screen recording tools you can't do this so easily.