AV1 vs H.265 HEVC for storage?

There has been a lot of buzz lately about AV1. An open source and royalty-free video codec developed by the ​Alliance for Open Media, a non-profit industry consortium.

In the same time my TrueNAS storage server is almost full at 80% occupied capacity. Мuch of that has been taken up by 4К videos from recent years. So I am currently thinking about how I can reduce this space. The videos are random clips from here and there, travel and family memories for example, they are not intended for future editing. So I can reduce their quality with a modern codec. But which codec? At the moment the two most popular codecs are AV1 and H.265 HEVC.

00:00 - Intro
00:45 - AV1
01:16 - H.265 HEVC
02:19 - Use case
03:06 - Testing