With the upcoming launch of the Nexus Q, which lets you stream Google Play content to your TV or stereo, Google will compete more directly with Amazon and Apple in a media-store melee where price is taking a backseat to how and where consumers can play what they buy.
Using both a computer and a tablet linked to each store, I checked out the online media markets run by these Internet behemoths. I used a Kindle Fire for Amazon's music and video stores, an iPad for Apple's iTunes, and an Android tablet for Google Play.
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Apple Has the Most Content
I found, first of all, that Apple continues to have the biggest catalog of music and video offerings--more than 28 million songs and 45,000 for-purchase movies as of April, and more than 85,000 TV episodes as of last October.
Amazon's MP3 store hosts more than 20 million songs, and an empty search of its Instant Video store indicates that it has more than 52,000 movies. It's difficult to gauge the number of TV episodes available there; the search shows more than 9000 TV titles, but titles may encompass entire seasons in some instances.
Google is far less specific about the size of its catalog, but it clearly trails the other two. Publicly, Google says only that it has "millions" of songs and "thousands" of movies and TV shows.
Varying Pricing Models
Prices for current releases were the same at all three services: You can rent movies in standard definition for $3.99 each or in high definition for $4.99 each, or you can purchase them for $14.99 (standard def) or $19.99 (high def). In the music markets, current albums go for $10.99 apiece and singles for $1.29 apiece.
Nevertheless, I found considerable variation in the pricing of older movies, TV shows, and music. Google Play, for example, offers a free song every day (presumably to attract you to the store).
Amazon Prime members can stream thousands of movies and TV shows to a computer, a Kindle Fire, an XBox 360, or another supported device free of charge: I used the service on a Kindle Fire to watch the 1954 version of Sabrina, which costs $2.99 to rent and $9.99 to buy on Google Play and on iTunes. Not all devices that support Amazon Instant Video also support Prime Instant Video, however. For example, my TiVo DVR, which offers access to Amazon Instant Video, can't stream Amazon Instant Prime content.
Playback Options Differ
Regardless of what you pay, you don't always get the same playback options--especially with video. For example, if you rent the film Mirror Mirror on iTunes, you have 30 days to start watching it, but once you start, you retain access to it for just 24 hours. Amazon and Google Play offer the same 30-day interval for initial access, but the window for watching it once you've started the video is 48 hours. These limits vary from title to title, in part because Hollywood studios dictate them--and the studios are still scrambling to figure out how best to monetize their content.
More significantly, though you can instantly stream iTunes purchases to Apple TV, the iTunes store does not support instant streaming of content to iOS devices--iPads, iPhones, and iPod Touch players--which means that you have to download the (purchased or rented) content first. Both Amazon Instant Video and Google Play, by contrast, can start streaming purchased or rented content on compatible devices immediately. Even if a device doesn't support streaming of Amazon content, Amazon's download technology usually lets you start watching it within a few minutes, as it continues to download.
Amazon Service Available on More Devices
Device support is a big differentiator. Amazon Instant Video is available on an impressive number of devices besides the Kindle (including computers, smartphones, tablets, set-top boxes, game consoles, and TVs); but you need either a desktop-grade browser or an Android device to watch Google Play videos. This holds true even for the Nexus Q, which requires an Android device to serve as its remote control. But even without a Nexus Q, you might be able to watch Google Play content on an HDTV if you have a device equipped with an HDMI output.
To play videos from Apple's iTunes store, you need an iOS device--an iPhone, an iPod Touch, an iPad, an Apple TV, or a computer running iTunes. Apple also sells a $39 dock-to-HDMI connector that, in theory, lets you watch iTunes video on a big screen without having to invest in an Apple TV. But user reviews are decidedly mixed on how well it works.
Options for high definition (HD) versus standard definition (SD) video vary, based both on device support and licensing considerations. Apple offers all videos in both SD and HD--if such versions are available from the content provider--because the iPad and current iPhones and Apple TV support both.
The Kindle Fire and most Android devices don't support HD video; however, on the Kindle you can still rent or purchase videos in high def when such versions are available, in case you want to switch to a device that supports HD playback.
Google Play offers less HD content than its competitors. At this writing, for example, Google Play has no HD option for Mirror Mirror, which you can get in HD on the other services. According to Google's documentation, studio licensing agreements dictate HD availability.