I was curious, so I looked it up. AV1 is more efficient than HEVC by like 28%! On the downside, encoding is horrifically slooow. It'll be interesting to see how much hardware support AV1 gets in the coming years, because encoding time will have a dramatic effect on its adoption rate.

Interesting to note: AV1 can be played in Kodi, Plex, Emby, Jellyfin, VLC, Chrome, Firefox, Edge, and Opera. So on the software side, it's pretty widely supported.