Spotify is "everything" which means Spotify is nothing. There's very little on Spotify I'm interested in listening to because it's so inclusive of everyone's excessively boring taste that it has everything you've never wanted to listen to.

Drip.fm is curated - it is one label's choice of the music that they vouch for so much that they are investing in promoting it. If you like that label, you are likely to like most of their music (but not all).

I subscribe to Ghostly and Stone's Throw - Stone's Throw because I got a freebie for discussing things with the guys who run Drip.fm (who also started Ghostly). Stone's Throw is not for me, so I don't mind that the subscription is dying off. However, they also have 6 Degrees, which is so fundamental to my listening habits that "6 degrees" is a genre in my iTunes.

Spotify is for "I feel like listening to that track I know that everybody knows." Drip.fm is for "I feel like finding new music."

You will not find this on Spotify unless you look for it. And "looking for it" is everything that's wrong with music these days. I'm on 5 different trackers - there isn't an album on the planet I can't steal. Yet I pay Drip.fm $15 a month to find me new music, and consider it a bargain.