They're similar, but subtly different.

Say Bob pays a $5 subscription and listens exclusively to artist Foo, 100 song plays. Alice pays a $5 subscription and listens exclusively to artist Baz, but plays their songs a whopping 300 times.

If it was paid out per user, Foo and Baz would both get $5. But paying out based on overall listener numbers, Foo would get $2.50 and Baz would get $7.50.

Essentially, it's a zero sum game, and one artist getting a play takes away revenue from every other artist. Even if you exclusively listen to your favorite artists, the vast majority of your subscription money is going towards the top artists.

This is why Spotify is always pushing their own playlists, smart shuffle, and encouraging background listening with ambient / sleep playlists and such; the more they can shift listeners toward music they've produced themselves or have special license agreements with, the less they have to pay out to typical (i.e. smaller) artists using their platform.