Spotify all the way with me.
They are the only ones who allow their users to use both playlists AND folders to organize their music.
Love using the folders because it works exactly like the Windows Explorer or Macintosh Finder.
You can for example start by have genres (classical, jazz, pop, rock, workout, dinner, movies etc) and then sub-folders from there and even sub-sub-folders if you want.
In my case for example I have a Classical folder with composers inside it and then the works.
So the Classical>Mozart would have sub-folders of Symphonies, String Quartets, Piano Trios, Concertos etc.
LOVE it!!!!
Totally awesome and best way for me to keep my music organized.