> if there is any advantage to JPEG XL over WebP or [AVIF]
Of course there is. Better compression than WebP, and unlike AVIF, it supports progressive decoding, which is super important for users on a slow network. Although AVIF can sometimes produce 50% smaller size files than WebP, many site owners will opt for WebP anyway because it has progressive image decoding, so their website will display something while an image is nothing rather than nothing until the whole image is loaded. With that said, JXL achieves comparable compression to AVIF, and it suffers way less from generation loss, too.
Of course there is. Better compression than WebP, and unlike AVIF, it supports progressive decoding, which is super important for users on a slow network. Although AVIF can sometimes produce 50% smaller size files than WebP, many site owners will opt for WebP anyway because it has progressive image decoding, so their website will display something while an image is nothing rather than nothing until the whole image is loaded. With that said, JXL achieves comparable compression to AVIF, and it suffers way less from generation loss, too.