Amazon.com (AMZN 3.32%) is the latest of the major tech firms to release a set-top box, joining a crowded market alongside Apple (AAPL 0.33%) TV and Google's (GOOG 9.98%) Chromecast. While these devices may not be of major importance to the companies' respective bottom lines, they do serve to extend their content ecosystems into the living room.

With still relatively little uptake, it's a market that remains open for grabs. How do these three products compare?

Interface
Apple TV has a fairly standard interface, one that should be easily understood by just about anyone capable of operating a television. Like the iPhone and the iPad, Apple TV offers up a simple grid of icons, each representing a different app. Clicking on an app brings up that particular app's content.

Amazon's FireTV is similar, but with a heavy emphasis on Amazon's own content. Vertical rows offer up categories like "movies" and "TV" populated with selections from Amazon's Prime video service. Third-party apps are there, but kept in their own individual row, accessible in a similar way to the Apple TV.

Google's Chromecast, in contrast, is dramatically different, lacking its own dedicated interface. Once you've set it up and turned the TV to the proper input, you must use your smartphone or tablet to control it. For someone technically inclined, this is fairly straightforward, though occasionally annoying, and I can imagine it being quite confusing to the typical user. Rather than having a set Chromecast app, you must have each individual app (HBO Go, Hulu, etc.) installed on your smartphone or tablet. Within these apps, you can tell them to send the content to Chromecast, rather than playing on your device's screen.

Of the three, Amazon's Fire TV is the winner. Compared with the Fire TV, Apple TV is slow, with a noticeable lag between button presses. The FireTV also offers voice control, which Apple TV lacks. Amazon's device could be improved to offer a greater emphasis on third-party content, but the grid of third party apps is no different than what Apple TV is offering. Google's Chromecast comes in last for its reliance on a separate device.

Pricing
Pricing is pretty straightforward: Google's Chromecast, at $35, is the indisputable winner. Apple TV and Amazon's FireTV are tied in second place, each at $99. For that $99, both Apple and Amazon give you the device, a remote and a power cable. Google's Chromecast plugs directly into the TV's HDMI input.

App availability
In terms of pure numbers, Apple offers the most third-party apps (more than 30 in total). Google's Chromecast has about half that, and Amazon's FireTV has even less. Still, it's a bit of a toss-up between the devices, as the apps offered vary.

Amazon's FireTV, for example, is the only device capable of streaming Amazon Prime Video, the second most popular streaming video service. It's also the only option for Showtime Anytime, the Internet-based version of the premium cable network. However, it's currently lacking HBO Go, available on both Google's Chromecast and Apple TV.

Both Amazon's FireTV and Apple TV offer WatchESPN -- a service Google's Chromecast doesn't have. Apple TV has many other network video apps, including the History Channel, WatchABC and the Disney Channel, not available on the other two.

Audiophiles might prefer Google's Chromecast over the others, as it does offer up more in the way of streaming music services (Rdio, Songza, etc.). But those who have purchased a lot of music through Apple's iTunes or Amazon will likely prefer their respective devices.

Amazon's FireTV is capable of playing video games, a feat unmatched by Google's Chromecast and Apple TV. However, to really take advantage of the feature, you must purchase a separate $40 controller, and at least for the time being, there are no must-have games.

No clear winner
After testing all three devices, I can't say definitively that there's a clear winner.

Google's Chromecast is offered at an unbeatable price, but its arcane control scheme limits its appeal. Amazon's FireTV wins on the interface, but is held back by a lack of apps. Apple TV has the most content, but it's sluggish compared to the FireTV, and Amazon's increasingly impressive Prime video service is nowhere to be found.

Unlike smartphones and tablets, which are already showing signs of maturity, Internet-connected set-top boxes remain in their infancy. Until a device that's clearly better than its rivals emerges, the market remains wide open.