Comment by IvanK_net

You can have a PNG and JPG versoin of the original image without no loss, and the files would be about the same size.

You can have a PNG and JPG version of the original image, with the same loss - "average error per pixel", and the files would be about the same size.

I know there is no lossy compression described in a PNG standard. But there exist programs which produce tiny PNG files with a loss. So comparing an MP4 encoder with a bult-in loss to a PNG encoder without any built-in loss is not fair. They should have made the MP4 encoder encode the video in a lossless way, just like they did with PNG.