Android Lollipop offers much more granular control over application alerts and notification settings, as well as advanced controls to "pin" certain apps to your lock screen and limit the amount of information that's displayed on your locked display. You can also deem other compatible Android devices "trusted" using the Android Smart Lock feature, so your Lollipop phone or tablet remains unlocked while in range of the trusted gadget.
These are just a few of the unique features available in the Nexus 9 version of Android and not in the Fire OS. (You can find a more detailed list of new Lollipop features on Google's website.)
The Kindle Fire HDX 8.9 could at some point be updated to a tweaked version of Android 5.0, but even if it is, the software will be so heavily customized that it's impossible to predict which features will be available and which will be blocked. That's the real value of buying a Nexus device: You know that a carrier or third party, such as Amazon, won't block or modify any of the features or functionality that Google purposefully builds into its versions of Android.
The Fire OS is great for certain things -- namely consuming Amazon content. Compared to the user experience of the Nexus 9, however, it feels simple, which is OK, and both limited and a bit long in the tooth, which is less OK.
2) Nexus 9 Has 50 Percent Bigger Battery Than Kindle Fire HDX 8.9
The Nexus 9 has a significantly larger battery pack than the Kindle Fire HDX 8.9. Specifically the 6,700mAh battery in the Nexus 9 has a capacity of nearly 50 percent more than the 4,500mAh battery in the Kindle Fire HDX 8.9. In my experience that doesn't exactly translate into 50 percent more battery life for the Nexus 9, probably because both devices have a number of battery-saving technologies that kick in a different times. I read Kindle books on both devices, with the screen brightness set to auto based on the system brightness, for multiple hours at a time, and the Fire HDX does seem to last notably longer during constant, heavy use.
3) Nexus 9 Has 64-Bit Processor Compared to Fire HDX's 32-Bit CPU
The Kindle Fire HDX 8.9 packs a slightly faster processor (2.5 Ghz Snapdragon) than the Nexus 9 (2.3 Ghz NVIDIA Tegra). However, speed isn't everything.
The Google Nexus 9 is the first Android tablet with a 64-bit CPU. The Kindle Fire has a 32-bit CPU. In other words, Google's Nexus 9 can run 64-bit Android apps, Amazon's Kindle Fire HDX 8.9 cannot.
What does that mean? According to NVIDIA, the beefy CPU should ultimately translate into "PC-class performance, extended battery life and great Web browsing."
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