While this is just a quick and superficial encoder comparison, I tried to keep it close to practical applications. From the VP9 vs HEVC test here, libvpx-vp9 is able to take on x265 when it comes to coding performance. Please note that only these encoders were tested and there are other AVC, HEVC, and VP9 encoders out there which may perform better.

If you have additional inputs to the test please reach out to me! I am very willing to run this again using a different set of settings.