All three of these music-streaming services have a lot of interesting and helpful features to bring the sweet nectar of music to your ears. I use all three and recently started thinking about the benefits of each, and how to describe them. I might get some people heated up over this topic, so please feel free to share your thoughts, or suggest another alternative. 

Pandora

http://www.pandora.com

Pandora is by far the most popular of these three and with a simple interface and large music library it's easy to see why. Pick an artist or song and it populates the music you might like. If you like or dislike a song you can hit the thumbs up or thumbs down button. But my favorite feature is the lyrics and band information listed below the player. Great for days when you know exactly what you want. 

Ad-free service: $4.99/month.

iTunes Radio

https://www.apple.com/itunes/itunes-radio/

iTunes Radio is built into Apple's own iTunes application and features a tuning control slider to favor more popular songs ("Hits"), or more obscure ones ("Discovery") or something in-between ("Variety"). But my favorite feature may or may not be yours: If you have speakers set up around the house using Airplay you can stream iTunes radio to all of the base stations at once. This is amazing for hosting a party when you want to fill your house with the same music. The other services here can't do that. 

Ad-free service included with iTunes Match, $24.99/year.

Spotify

https://www.spotify.com/us/

Possibly the edgiest and most fun of the three, I love Spotify's organization of musical styles and genres. You can play music from playlists such as "Mixed Generation Party", "Focus" or even "Hangover Friendly". Also I must say the music selection is exotic but user-friendly - I just recently started listening to Spotify and I am a huge fan.

Ad-free Service: $9.99/month.

In conclusion:

1. When I'm throwing a party: iTunes Radio
2. At work and when I know what I want to hear: Pandora
3. If I'm bored and up for something new: Spotify
4. And if I had to pick just one... iTunes Radio.