(1) The tests on icons is really not fair, I mean, PNG is always going to win on that kind of image.
(2) It is little realized that AVIF kinda sucks for high-quality photographic images. I mean, if you are making a hero image for your blog and you want it to be big and fast loading and it doesn't have to stand up to close inspection it is great. If you took it with your mirrorless and you want it to look like you took it with a mirrorless you do very well with JPEG or (better) WebP. I mean, AVIF is meant for encoding video where people don't look closely at individual frames. JPEG XL rules for high quality photographs.
JPEG XL, the New Image Format Nobody Wanted or Needed (2021) · HackerTrans
(2) It is little realized that AVIF kinda sucks for high-quality photographic images. I mean, if you are making a hero image for your blog and you want it to be big and fast loading and it doesn't have to stand up to close inspection it is great. If you took it with your mirrorless and you want it to look like you took it with a mirrorless you do very well with JPEG or (better) WebP. I mean, AVIF is meant for encoding video where people don't look closely at individual frames. JPEG XL rules for high quality photographs.