Worse as in not compressing as well. As I said, at high fidelity or lossless. At lower quality levels, AVIF files are smaller and JXL files are bigger. At higher quality levels, JXL files are smaller and AVIF files are bigger. At lossless, AVIF is worse than PNG, while JXL is much better.
> Like implied I'm not an expert, I'm just wondering why AVIF can't have faster loading with a preview function like JPEG has.
JPEG is fast to load regardless of its progressive loading feature. So there are really two things at play, speed of decoding, and whether partially loaded files can give you a preview. The slow decoding of AVIF is inherent to the design of the format, but different encoding choices can lead to different decoding speed. IIRC, the lower the encoding quality, the faster the decoding can be. And as for progressive display, that simply wasn't considered when AV1 was designed. You can do something funny and store two AVIF frames, one low quality and maybe lower resolution, followed by the full image, but then you're storing two images just to get a preview.