We were at the NAB show in Las Vegas last week, giving demonstrations to many of the companies attending, showing x265 encodes of popular video sequences side by side with x264 encodes (the gold standard for quality today). Attendees were blown away by the quality of x265. We demonstrated 2 streams played back in sync, showing the middle 50% of two 4K clips on a 4K monitor. Here is a photo of our demo...
Sample frame grabs from Crowd_Run4K50 @ 4 Mbps are here...
http://x265.org/CrowdRun4K_4Mbps.7z
You can repeat these tests yourself, using the SVT clips from
http://media.xiph.org/video/derf/ - Crowd Run, Old Town Cross, Ducks Take Off, In To Tree.... take your pick.
H.265 provides for much higher video coding accuracy. The thing you will notice is that x265 encodes don't have all of the temporal artifacts of H.264. x265 is typically winning comparisons against x264 even at half the bit rate. There were cases where x265 was preferred even at 1/4 the bit rate
(Crowd Run 4K - x265 veryslow 4 Mbps vs x264 veryslow @ 16 Mbps), due to the lack of temporal artifacts and macroblocking in x265.