I don't understand the difference in your two propositions, since money is fungible : whether the ratio is established globally or customer per customer, the end result would be the same, wouldn't it ?
Unless there are specific calculation rules ?
What Spotify actually does is give these two artists some cents per play. Let’s say $0.01 per play, they each get $0.20 from my subscription and the rest of my $10 goes to Spotify.
It's really unclear whether an artist-centric model would make any real difference to artists - under an artist-centric model the more an individual user streams the less the artists get per stream, so if you have a small number of fans who listen to you a LOT the artist-centric model means you get less money