This week, Nielson released its “Music 360” report, revealing that we still use the radio as our primary music discovery method. So who’s winning when it comes to Internet radio? In the world of ad-supported free radio there are many websites to choose from. But boil it all down and you’ll find yourself torn between two: Slacker vs Pandora.

[Looking for savings that adds up every day? Apply for a PerkStreet account and earn cash back on debit card purchases!]

Sure there are niche sites for specific things. Millions of them. I love listening to LoudCaster when I’m in the mood for something curated by a single DJ, as an example. But when it comes to the mainstream debate, the key players for finding new jams are clear. It’s Slacker vs Pandora all the way.

Let the Slacker vs Pandora debate begin!

Slacker vs Pandora: Lots in Common

There are a lot of commonalities when it comes to comparing Slacker vs Pandora. Both allow unlimited free streaming of music, which is supported by regular audio ads that play between songs — and both also have have paid upgrade options.

Both of them allow you to customize your experience by entering a song, artist or album into a search field. When you do, both players respond by generating a multi-artist playlist for you, based on your preferences.

While you’re listening, you can give both players feedback about what you’re enjoying and what you don’t like, which further customizes the experience. In the free versions of both, you’re limited to 6 skipped songs per hour.

Finally, both Slacker and Pandora have high quality web interfaces and mobile versions spanning devices so you can listen to good Internet radio while you’re on the go. Now let’s get on to the Slacker vs Pandora deciding factors…

Slacker vs Pandora: Meet Slacker, the Underdog

• Monthly Listeners: ~1,500,000
• Total Songs: ~8,000,000
• Mobile Apps: iPhone, iTouch, iPad, Android, Windows Phone, Nokia, Palm

Slacker Radio, from a popularity standpoint, is the clear underdog in this debate. However, Slacker has more songs than Pandora. It’s only available in the U.S. and Canada. But Slacker also features a vast array of preset stations to choose from, something Pandora doesn’t offer.

Bottom Line: Slacker lets you build a more customized experience than Pandora. You can use it to create custom stations, which compile a blend of your favorite artists and offer new music that fits into a broad stroke. This lets you discover music that fits your taste really easily. You can also make Custom Playlists on

Slacker vs Pandora: Meet Pandora, the Incumbent

• Monthly Listeners: ~14,000,000
• Total Songs: ~900,000
• Mobile Apps: iPhone, iTouch, iPad, Android, Blackberry, Kindle Fire, Nook

Pandora has a massive number of regular listeners, making it a juggernaut when it comes to free online radio. On the down side, it only has about 1/10 of the total songs in its database. Pandora is available in the United States, Australia and New Zealand. Pandora is pretty much as simple and clean as a music player can be, meaning everyone pretty much uses it the same. This does not, however, mean it doesn’t offer an incredibly well-customized experience. It does, thanks to its algorithmic logic, which learns what you like.

Bottom Line: The Music Genome Project is what sets Pandora apart from Slacker. While you can’t build a customized station on the fly, each station you create on Pandora will gradually become more well-customized for you as you “thumbs up” and “thumbs down” songs. Even though there are fewer songs, each song on Pandora has been analyzed for over 450 unique musical characteristics, so it’s really well equipped to decipher why you like certain songs and introduce you to others you’re likely to enjoy.

Spotify and Jango also Belong in this Conversation

More and more, Spotify and Jango both belong in the debate over who’s the best music discovery website. Jango now has more monthly listeners than Slacker at about 2,000,000. Jango has gone a different direction altogether with music discovery, by allowing users to create stations anyone can access.

Spotify has an estimated 15,000,000 songs currently available. This site focuses primarily on letting you play music you already know you like (a different service altogether, but one worth exploring). However, Spotify also released its own radio service for music discovery in December. Spotify is growing in popularity, too, swelling from about 500,000 unique visitors per month a year ago to some 2,500,000 today.

Making the Choice that’s Right for You

So who’s the winner of the Slacker vs Pandora slug fest? Ultimately, you have to find the music discovery site that’s right for you.

If you want something fully automated, which you customize slowly and methodically to find the music you’ll like, check out Pandora. It may end up making better suggestions over time.

If you tend to find new bands with similar styles regularly, and want to find things that are similar quickly, try building a custom station on Slacker.

And if you try them both and neither is cutting it for you, check out Spotify and Jango. After all, the discussion doesn’t have to be just Slacker vs Pandora with so many other options out there.

In the meantime, happy listening. I hope you discover something great, wherever you find it.

What do you like more, Slacker or Pandora? Do you discover music through another site? Tell us about it in the comments below.