Every study I've seen shows AV1 beats H.265 on VMAF at all bitrates. H.265 never got significant browser support, and I don't expect H.266 to either. https://caniuse.com/hevc
I have seen a scientific paper a few weeks ago stating h265 was ~7% smaller than av1 on tested dataset. Although maybe it's dataset sensitive or differ because of the metric? (maybe it was PSNR or SSIM?)
Anyway any data on AV1 hardware decoding energy consumption vs h265? That is probably the main differentiating metric of interest here