Both JPEG XL and WebP far exceed AVIF when it comes to lossless. For lossy, AVIF used to do better at low quality and JPEG XL at high quality. But apparently AV1 encoders have improved a lot since then, closing the distance. An article comparing the two was posted recently:

https://news.ycombinator.com/item?id=49690554

The author, who has worked on said AV1 encoders, has expressed doubt that JPEG XL encoders could improve much with only reasonable amounts of effort, but that was also only their personal (if educated) guess. With JPEG XL finally seeing adoption on the web, we will hopefully see work on the reference encoder resume in earnest soon.

So for now, I’d say you’re fine with AVIF. Unless you’re doing lossless, because AVIF sucks at lossless. (And JPEG XL has the unique feature of supporting lossless JPEG transcoding, too.)