It’s more competitive at the high end, but this website has some comparisons of avif and jxl: https://svt-av1-psy.com/avif/

(this project was later incorporated into other encoders as tune=iq, and is now default)

That being said, I think the jxl bitstream does have a fair amount of potential that current encoders don’t exploit due to lack of manpower. I’ve been following development fairly closely over the past couple years on the jxl discord, I think all active jxl devs are there