DisplayMate recent held a display battle between the Amazon Kindle Fire HDX 8.9, the Apple iPad Air and the Nexus 10. According to DisplayMate's Raymond Soneira, not only did the Kindle Fire HDX 8.9 beat out the Retina display sporting iPad Air, it was actually the best panel ever tested by the company and had the highest brightness score ever seen during a DisplayMate battle...
Source: http://www.phonearena.com/news/Amazon-Kindle-Fire-HDX-8.9-beats-out-the-Apple-iPad-Air-and-Nexus-10-in-display-test_id49053
Source: http://www.phonearena.com/news/Amazon-Kindle-Fire-HDX-8.9-beats-out-the-Apple-iPad-Air-and-Nexus-10-in-display-test_id49053