Why is VP9 codec worse than AVC codec in HD quality?

[ArminW]

Hello guys!

When I upload my videos in 4K, and then watch them in Chrome, the HD Version of it looks really bad with a lot of artefacts. The HD Version in Chrome is transcoded by Youtube to the VP9 codec.
However, when I watch the same Video in Safari, or when I upload the video in HD, the Video looks much better. In these two cases the video was transcoded to the AVC (H.264) codec.

See for example here (watch in Chrome and set the Quality to HD if it is not set initially):

4K Version (Artefacts especially where the waves roll of at the beach):

HD Version:

Shouldn't it be the other way around, the newer VP9 codec giving a better quality than the AVC codec?
Does anyone have an idea in how to improve the HD version of a 4K Video?

Cheers,
Armin

 

[mirrorlessNY(youtuber)]

Hi Armin, welcome to the forum & congrats on 1st post. Are you watching these videos on 15" laptop?

 

[ArminW]

Hey! I am watching it on a Mac Mini and 13 inch Macbook. And also tried it on a Windows Laptop.

 

[mirrorlessNY(youtuber)]

how large is the screen on Mac Mini? try watching on a 4k TV or large 4k pc monitor

 

[ArminW]

When I watch the Video in 4K (on a 4K TV) it looks fine. The problem is, that the HD Version of the Video, which you get when watching it on a Laptop in Chrome looks bad. However the HD Version when watching in Safari looks better. Youtube uses different codecs for Chrome and Safari. VP9 for Chrome and AVC for Safari. VP9 is the newer codec which is supposed to look better than AVC, but its the other way around. This is what confuses me.
Does anyone have an idea why this could be?