Netflix Finds x265 20% More Efficient Than VP9 (streamingmedia.com)
Reader StreamingEagle writes (edited): Netflix conducted a large-scale study comparing x264, x265 and libvpx (Google-owned VP9), under real-world conditions, and found that x265 encodes used 35.4% to 53.3% fewer bits than x264, and between 21.8% fewer bits than libvpx, when measured with Netflix's advanced VMAF assessment tool. This was the first large-scale study to use real-world encoder implementations, and a large sample size of high quality, professional content.A Netflix spokesperson explained why they did the test in the first place; "We wanted to understand the current state of the x265 and libvpx codec implementations when used to generate non-realtime encodes optimized for OTT use case. It was important to see how the codecs performed when testing on a diverse set of premium content from our catalog. This test can help us find areas of improvement for the different codecs."
x265 is not very important except for 4K content and mobile phones
I think a 20% overall reduction in bandwidth for an in-demand and still-growing medium is *very* significant no matter what the resolution or device is.