How well does bcachefs handle databases and VMs? Those workloads are well-known to be btrfs' kryptonite whereas ZFS seems to tolerate them pretty well as long as one sets the correct recordsize (example: https://www.enterprisedb.com/blog/postgres-vs-file-systems-p...).
It's worth mentioning that bcachefs has gotten a fair bit of performance work since the last round of Phoronix benchmarks. Also there's some bug where the formatting tool selected 512 byte blocks by default instead of 4k byte blocks on drives where other filesystems picked 4k bytes, which impacted the Phoronix benchmarks. Unsure if that has been fixed yet.
NoCOW on btrfs is a kludge because it disables the core features of btrfs and is dangerous to use with raid1. Since, ZFS doesn't even have a nocow mode, surely there are other ways of dealing with databases?