I must admit, I'm not sure why JPEG XL is viewed so favourably on HN, it's not something I know a ton about, but my understanding is that the big advantage of AVIF is that you can reuse hardware decoders built into devices for AV1 for the images.
It being a strict improvement over JPEG is nice for the developers not having to go back to the source image for an upgrade, but that seems like a pretty small benefit that only matters during the transitional period.
Meanwhile, if you are getting better battery life every time someone views an AVIF image, that's a huge benefit for the entire lifetime of the format, it seems to massively outweigh any advantage JXL has, to me.
It being a strict improvement over JPEG is nice for the developers not having to go back to the source image for an upgrade, but that seems like a pretty small benefit that only matters during the transitional period.
Meanwhile, if you are getting better battery life every time someone views an AVIF image, that's a huge benefit for the entire lifetime of the format, it seems to massively outweigh any advantage JXL has, to me.