Tablet Review: Amazon's Fire vs. Google's Nexus 9

New tablet computers from Amazon and Google both run on Google's Android operating system, but that doesn't mean they work the same. In the new Fire HDX 8.9, Amazon continues a practice of modifying Android extensively to drive you to Amazon services. Google Inc.'s new Nexus 9 offers as pure of an Android experience as you can get — which means driving you to Google services.

Two tablets. Good for different reasons. Customers will need to decide: What do they want a tablet to do?

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AMAZON FIRE HDX 8.9 (Starts at $379)

What's New: Apps open slightly faster and sound is much better in this year's version of the tablet. There's less distortion using speakers. For headphone use, the new model supports Dolby's Atmos technology for three-dimensional sound, though Amazon's video service is only starting to make Atmos movies available. Amazon is also bringing the Firefly feature introduced in its Fire phone over the summer. Firefly uses the device's camera to pull out phone numbers, scan bar codes and even identify everyday products — which you can then buy through Amazon. You can use it to compare prices in retail stores, but its size makes it difficult to stay discreet.

Also new — Amazon now lets you share tablets with separate profiles for two adults and four kids. The kids' profiles offer time limits and other restrictions, such as playing games only after spending a half-hour on educational books. An upcoming update also will let you share Amazon content across multiple devices, similar to what Apple has done with its Family Sharing feature.

Even without a major change from last year, you're still getting one of the sharpest displays, at 339 pixels per inch. The Fire is also lighter than Apple's super-light iPad Air 2, though you're also getting a smaller screen at 8.9 inches, as measured diagonally, compared with the iPad's 9.7 inches.

Like the previous model, the Fire offers one-button access to live customer support. Amazon's Mayday advisers appear in a video box on your screen and can help you find apps, operate the camera or figure out why something isn't working properly. It's a great tool for the less technically inclined.

What's Unique: What distinguishes the Fire most is its tie-in to Amazon.com Inc.'s services. The home screen offers quick access to Amazon videos, songs, e-books and shopping. If you use a lot of Amazon services, the Fire is the tablet for you. If you want to stray from Amazon services, you might run into problems. Many leading apps are available, but it's not the full selection available with Android. For instance, I wasn't able to download Android apps to check my personal bank account or to track results for Sunday's New York City Marathon. I used Google's Nexus 9 for both.

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GOOGLE NEXUS 9 (Starts at $399)

What's New: The Nexus offers you a taste of Lollipop, the latest version of Android. Lollipop lets you interact with email and other notifications right from the lock screen, and it lets you unlock the device using the presence of a trusted device, such as an Android smartwatch. Like other Lollipop devices, the Nexus supports multiple profiles — up to eight, with no restrictions on which are for adults. A swipe from the left gets you the Google Now virtual assistant, if you've turned that on.

Made by HTC, the Google-designed device is slimmer and lighter than the previous Nexus 10. The dimensions have changed to match the iPad's and are now better for viewing photos, Web pages and documents. The Nexus also comes with a near-field communication chip, enabling mobile payments through Google Wallet. Apple's iPads lack this chip and allow Apple Pay only for online purchases. That said, I promise to make fun of you if I catch you waving a giant tablet to pay for groceries.

By Comparison: The new dimensions have created a lot of wasted space when viewing video, unlike on the Fire and many other Android tablets. Audio wasn't as loud, video as bright or text as sharp as on the Fire at maximum settings. Google clearly tries to steer you to its services, with the default home page icons consisting entirely of Google apps such as YouTube and Gmail. But there's a vast selection of other apps you can install. Although many apps still come to Apple devices first or have more features for them, most Android apps work on the Nexus — but not necessarily the Fire.

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SO, WHAT TO BUY?

Apple's iPad Air 2 and Samsung's Galaxy Tab S go further than the Fire HDX 8.9 and Nexus 9 in letting you unlock the devices with fingerprint IDs. The Galaxy's screen produces richer colors than most tablets, while the new Air is alone in having an anti-reflective coating to reduce glare. But both start at about $500.

The Fire and Nexus devices are more affordable and should meet many people's needs. The Fire is great for those newcomers, thanks to its Mayday help offering. Those newcomers — along with casual users and Amazon power users — also might not mind the reduced app selection. But if you need to do more at this price point, the Nexus 9 is likely for you.