Distrokid, to me seems like the best online music distribution option out there. Of course there’s many ‘better’ options for different people but they would have to take in to consideration their personal goals. One of my favorite things about Distrokid is that you can upload an unlimited amount of songs for only $19.99/yr. They have super quick uploads to iTunes (2-4/hrs). They’re commission-less. They’ll also email you along the entire process so you know when your product is live on other websites. However they only upload to: iTunes, Spotify, Amazon, Google Play, Beats, Deezeer, Rdio, YouTube Music Key, and Shazam. They pay you monthly too unlike a lot of their competitors. If you create a lot of music and are uploading constantly this would definitely be the way to go, if you ask me.
Oh, and Derek Sivers (founder of CD Baby) and Jeff Price (founder of Tunecore) highly recommend Distrokid. (Both are no longer working at those companies).