Here is my little (3 samples) VP9 vs x264 test. Not very representative (need more samples) but at least I didn't used parkrun / park_joy for test which were criticized as insane.
Here is archive xls-files with metrics and plots:
VP9_vs_x264_metrics.zip
And here encoded samples with cmd-files I used for encoding:
VP9_vs_x264_samples.zip
P.S. Sorry, no time to make screenshots or to make formatted post with tables so download archives.