Winner, Spotify.
Okay okay, maybe it's not that simple. Perhaps there isn't enough information about each of these services to simply declare one BEST, especially without the ability to even use all of these services. Some of them aren't even available yet, I know, but they all will be soon. Lets give this all some context though, because there are some important factors to note.
First off, and I'm writing from my personal perspective as a vinyl collector/enthusiast and a genuinely whole-hearted appreciator of music, I think that all of these services provide something that is incredibly valuable. They really are fantastic, and although most of them have some underlying similarities, there are some lines drawn in pricing and options that will help you choose between them. If all of the services were the same, and you could just compare the price with the cost, well then this article wouldn't be necessary... but, each one of these is a variation on a theme (to get you streaming music that you want to hear), with mostly the same libraries of music just served up a little bit differently in each case. I'll try to present you an unbiased opinion (I'm an Apple guy, so consider that idea a joke) of what the services really offer, as well as my thoughts on what really matters with each. Understand that I do not recommend using streaming music from the internet as your single source of music exposure. I collect vinyl as my most common consumption of music, and I try to attend as many concerts as reasonably possible in an effort to support artists. For as much art and entertainment (and pure enjoyment) that artists provide to me, I consider it an honor to support them directly in the way that I do.
Now, with that said let's talk about the best streaming services available on the internet.
Spotify
If I had been able to use Spotify when I was in college, I would have saved myself a minimum of $6,000 just figuring out what kind of music I would now claim as my kind of music. There was a time in my life when I drove to Best Buy no less than once a week (usually on Tuesday) and would buy, on average, between 2 and 3 albums a week. If I was lucky, they only cost me $10 each. "How were you able to afford that much music?" you might ask. Simple, I couldn't. But I made it happen. And boy-howdy did I ever buy a lot of garbage in the process. Actually, I did buy Garbage. And, I bought Hoobastank. And I bought Mariah Carey, Fat Joe, and Jagged Edge. I'm not implying explicitly that all of those artists merit your ridicule... but I mention them in the context that they no longer fit into the wheelhouse of the music I listen to when I have a choice. It would have been great for me to have been able to figure all of that out without needing to purchase each of those albums. You might argue I didn't need to purchase all those albums, especially in the timeframe I was in college... I probably still could have downloaded them for free. You see, I thought I was respecting artists and their craft, and the ill-advice of Rollingstone magazine... but I was putting myself upside down in the process becoming a veritable hoarder of music in the compact disc format. Silly me. For $240 over the course of 4 years, I could have had all of that music from those 650+ CDs without added debt, and the shameful reality of having a Creed album on my shelf. That is, if Spotify had existed then.
Spotify offers users a free service (with occasional ads) with access to their entire catalog of 20+ million songs.
It's a free service.
The charge is nothing.
It is completely free.
If you have no money, but you want to experience new music all the time, for the rest of your life, you've arrived. It exists. You lucked out. Save your $40+ a week and figure out what music you like on Spotify, chances are they have more than you'll know what to do with.
The thing that's incredible about Spotify is that there is none of the radio pretense which surrounds the other services. If you want to listen to the new Deerhunter album, they've got it. If you want the new Daft Punk album, the day that it is released mind you, they've got it. Occasionally some artists or record labels will hold out for (*gasp*) an entire week before a new album is available on the streaming service (for FREE!), but that is a small price to pay (in time) for unlimited listening under your own control for the rest of your existence. For the free service, you will have to put up with what I consider to be modest advertisements, but nothing crazy. For $5 a month, just FIVE DOLLARS A MONTH, you can have all of that same music, ad-free. It is important to note that the music is only available on your laptop or desktop computer... but for $5 a month and the amount of time you spend on your computer in a month, this is still an incredible deal. Want to take it up a notch to complete baller status? You can spring for the $10 per month premium plan and get unlimited access to all of the 20+ million songs on all your computers as well as your iPad, iPhone, iPod touch, or whatever competitor you might be clutching every moment of the day. Unlimited streaming on all those devices as well as your computer, $10 a month. I'm beside myself that such a thing exists and people would chose not to use it.
I'm telling you, Spotify makes it seem silly that you would even try to hoard an mp3 collection (don't get me wrong, I'm keeping mine), because it's not even worth the time to take the music for free if you're still into that sort of thing. Just download Spotify and go nuts. Don't get me wrong, Spotify certainly doesn't have everything. So far no service has everything, but at 20 million songs and growing, Spotify is money well spent. Oh yeah, and one last note, with spotify premium you can save music to your devices to listen to when you don't have an internet signal. Another option I cannot believe exists. Right on, Spotify.
Did I mention I like Spotify?
Pandora
Pandora is an incredible online streaming service. It boasts the longest history of any of the services discussed in this article and easily the largest subscriber base of any so far. Easier to do when you've been around 10 years like they have. They tout some pretty large numbers in regard to subscribers, but it's important to note that I'm technically a subscriber and I haven't used Pandora in at least 3 years. Regardless, Pandora is another free service (with ads) that is powered by the Music Genome Project. It allows users to stream music to their computer or handheld device and, up to a certain extent, skip songs that they don't like, favorite songs that they'd like to hear more often, and discover new music or similar music to artists they already like. There are limitations, you can only skip so many times before you are forced to listen to whatever comes next (or turn it off)... and if you use the free service you've got to listen to those occasional ads. Again, not bad. Pandora is actually REALLY good at making radio stations out of artists you love, out of albums you love, and out of era's you love. Put on the Vanilla Ice radio station next time you're on Pandora and prepare to be delighted (it wears off quickly, I promise).
For $4 a month (or $36 annually) you can get Pandora ad free. It's awesome. $4 a month for ad free music. Only trouble is if you pick the Michael Jackson radio station, you can't just listen to all MJ all the time, you have to pay your respects to the other artists that come up on that station before you get to another Michael Jackson track. For free or fee though, it's still not a bad option. My Mom loves Pandora, I used to love Pandora. A lot of my friends love Pandora. It's probably great for work. I don't know. It's no longer for me because...
iTunes Radio
Yeah, I know I know, this service isn't even out yet and was literally just announced two days ago as I write this. iTunes Radio is Apple's attempt to break into the streaming online music service world and get a little piece of the action.
I will use iTunes Radio. Probably a lot.
How can I be so sure? It's going to be automatically integrated into iOS 7 this fall when Apple updates the operating system of my iPhone and my iPad, it will have the largest selection of music compared to these competitors, it will probably have unbelievably great music recommendation logic, and it's built-in radio stations will, without a doubt, be top notch stations to listen to at any time. It will be a free service (with ads) and will be ad-free with a subscription to iTunes Match which is a $25 a year service (cheaper than pandora, mind you) and is an incredible benefit in and of itself without the iTunes Radio part.
As I said, I will use iTunes Radio all the time.
Like Pandora, it is 'radio' based in that you can't just select an artist and exclusively listen to that artist... you must listen to other music/artists before you'll hear that second Michael Jackson track... but like Pandora, you can give the music you're hearing a thumbs up to hear more music like that song, or you can select "never play this song again" if it was a complete miss based on your interests. Pretty stellar. It will undoubtedly be a beautiful and easy-to-use interface, and for a mere $25 a year ad-free... it will be the easiest decision I make since I'm already using iTunes Match with nothing but good things to say about it. Finally, like Pandora, iTunes Radio will also be available on my AppleTV, and thus, through my stereo in my living room. Double bonus.
Sorry Pandora, I just don't see where you fit in anymore.
Now that said, if you don't have a house and pocket full of Apple products like I do, don't get me wrong, maybe there isn't enough incentive for you to just whole heartedly adopt the new service. Why change service when Pandora already has all your radio stations trained exactly how you want them? No doubt. Keep Pandora, I'm not asking you to change or trying to convince you of one's supperiority over another (okay, maybe I am), but I will say that iTunes Radio will probably be largely successful just by association alone and will likely have a very large acceptance rate among it's already enormous user base. I cannot wait until it's available.
Google Play Music All Access
"Is that seriously the name of the service?"
Yes. How unfortunate.
Google just announced its competitor within the last month as well, trying to get their feet wet before Apple made their announcement this week. It's no coincidence. Like all of these services, Google touts a pretty large library of music to tap into (not as much as Spotify though, if you're counting), and is a great service. I don't know that it is any more competitive than the alternatives other than it's attachment to Google. Like Google+, it has had a seemingly slow adoption rate in it's opening weeks, but perhaps will see a rise in the future. Their service is $10 a month ($8 if you subscribe starting this month, early adopter) and gets you essentially the same kind of service you get with Pandora or iTunes Match. I think GPMAA (if I may) might have the best free service in that it is ad-free, free.. just with some limitations. The catch is, Google Play Music All Access (*sigh*) isn't even available yet on iOS devices. So no access via iPhone or iPad, which means a pretty huge audience will probably not even know it exists (especially with a name like that). Seriously, google it... ironically the link you're looking for won't even be the top search result IN GOOGLE. App quality, like all these services, is likely to be very high (I wouldn't know in this case, remember, I'm an Apple guy) and for 90% of the users (at least), all the music you actually want to be listening to will likely be available. So, if you ask me, it's just a choice for which service you chose. I suppose I should mention that Google Play Music All Access does allow for "unlimited skips" and does offer some pretty good access to the music in your "locker" across all the devices you may use. If that's your thing.
In Summary
There are choices here. Any choice you make will be a good one because any of these services will give you access to more music than you could possibly desire. All of them have large libraries of music to tap. Some of them will integrate more readily with devices you already use, some will cost you more than others (but probably with a free option), and one (Spotify) will give you a little bit more control of your listening experience, but likely at the cost of the music discovery (radio) aspect that the others offer. If you're like me, you'll probably be happy to pay for Spotify AND one of the other three services (or at least use the free service) because it's nice to change things up from time to time. I am a Spotify premium user, a SiriusXm subscriber (both in my car and streaming on my handhelds), I will use iTunes Radio... and I will keep collecting vinyl like a boss, because that's how I get down.
One final note. I won't argue that there aren't some other issues in play on this topic. The truth about Spotify is that they pay the artists fractions of what they honestly deserve for music they provide. That part kills me. For the most part though, that is true about a lot of the deals that these services have struck with artists and record labels under no duress. The music industry is in a different place than it was 10 years ago and earlier, and nobody seems to see a clear picture for where it's going and how artists will be able to thrive in the current arena. This, however, is not your fight to fight fellow music lover. The reality is that the services exist, are completely on the up and up, are fantastic to use on mobile devices, and are at a price that is unfathomable compared to the previous options and availability. As a vinyl enthusiast, Spotify provides me the opportunity to spend some time with albums that I may be uncertain about before I blindly go out and purchase them. I buy a ton of vinyl, I love the format and I love physically owning my music... but now I buy it a little more selectively, because I can. For a paltry $10 a month, listening to music has never been easier or more accessible than it is right now.