Sheer quantity of music. I have yet to see another music service come close in content to youtube. Spotify is okay, but there's a lot they don't have. And th

Sheer quantity of music. I have yet to see another music service come close in content to youtube. Spotify is okay, but there's a lot they don't have. And their commercials are annoying as hell. Pandora is great, but their model doesn't allow for selecting specific songs. Soundcloud is awesome for original and underground tunes, but not mainstream and classic songs. Youtube has (almost) everything.