In addition Pandora is looking to challenge Apple Music, Tidal, Spotify, et all with a $10 subscription that would allow on demand music just like the mentioned giants of streaming music. But how are they going to attract people to Pandora, rather than the aforementioned services many of which have strong exclusivity deals already in place.
Spotify just released a Metallica documentary, Apple Music has upcoming Britney Spears album, and Google just has a massive user base on Android. We'll just have to see how Pandora will solve this puzzle.
The simple fact is that 99% of the catalogs are the same and it really comes down to how you get people to try it in the first place combined with how well the service actually works. The fact that they have a free option is a big advantage for the first part of that.