One of the most interesting things to me is that JPEG-XL is under an open Patent License, unlike the original JPEG.

https://en.wikipedia.org/wiki/JPEG_XL

Also, Google contributed quite a bit to it's development. As the patent grants show:

https://github.com/ImageMagick/jpeg-xl/blob/main/PATENTS

https://github.com/libjxl/libjxl/blob/main/PATENTS

Microsoft seemed to have gotten a patent on part of it's implementation (which Google also tried to get). Not sure if Google will pay to invalidate that patent, but I have a feeling they are more likely to defend AVIF.

https://www.theregister.com/2022/02/17/microsoft_ans_patent/

Google's control is a little concerning, but I do feel there are bigger fish to fry then choosing between two free formats. A bigger concern is the H.264 and H.265 patents domination of video.