YouTube has a different catalog with some overlap. There’s lots of stuff that you’ll find on any mersh service that you won’t find on YouTube.
I didn’t find the original recording of “Way Out West” by Big Star just now, but I did find a live version from 2008. Spotify has the original but not the new one, YT vice versa.
It took a little doing to find a recognizable song that wasn’t in some slideshow/record spinning video, though.
Next epic smash up fight on YT is about publishing rights on cover songs. I don’t think the computer science will support auto-recognition.