Earlier quoted context omitted.
Using any single artist as a barometer for library completeness is probably not a great metric.
I'm not saying it's something to rely on, but if the artist is: not American, not singing in English, not from the top hit lists, not from popular genre and published albums years ago... yet they get included in the library, that means the choice goes far beyond what you usually get to hear. And that's just a great thing, whether you like specific artist or not.
My point is just that both Rdio, Spotify, and all their competitors contain many bands that fit your criteria. And they also don't contain many of those. I'm simply saying you should do a wider survey of their libraries to get a better comparison.