That second link is remarkably hard to read. I hate this hipster web design trend of using faint text that barely contrasts with the background. That's so the opposite of what a reading experience should be.

Anyway, on VP9... its disadvantage is that it's very computationally taxing compared to H.264 (and presumably VP8). MS Edge won't use VP9 on laptops that don't have hardware decoding for it, because decoding VP9 with software kills battery life. Are other browsers following similar policies on laptops? (this is only applies when the laptop is running on battery, and Edge will let you force VP9 even on battery in its flags).

H.264 is quite elegant and efficient from a computational perspective. Note that even when laptops have and use hardware decoding for VP9, they still use more battery than hardware decoding H.264 (which will be in any computer that has hardware for VP9). Though there must be a threshold where a difference in bitrate would equalize them.

I guess the days of H.264 computational efficiency are over if we want better compression. I'll read your links to see what to expect from AV1.