I haven’t dug into the test data or methodology myself but I read a discussion thread recently (on Reddit - /r/jpegxl/comments/l9ta2u/how_does_lossless_jpegxl_compared_to_png) - across a 200+ image test suite, the lossless compression of PNG generates files that are 162% the size of those losslessly compressed with JPEG XL.
However I also know that some tools have bad performance compressing PNG, and no certainty that those weren’t used
It has a higher bit depth at orders of magnitude less file size. Admittedly it has a smaller max dimension, though the max for PNG is (I believe) purely theoretical.
Only thing I can think of is that PNG is inherently lossless. Whereas JPEG XL can be lossless or lossy.
I haven’t dug into the test data or methodology myself but I read a discussion thread recently (on Reddit - /r/jpegxl/comments/l9ta2u/how_does_lossless_jpegxl_compared_to_png) - across a 200+ image test suite, the lossless compression of PNG generates files that are 162% the size of those losslessly compressed with JPEG XL.
However I also know that some tools have bad performance compressing PNG, and no certainty that those weren’t used
It has a higher bit depth at orders of magnitude less file size. Admittedly it has a smaller max dimension, though the max for PNG is (I believe) purely theoretical.