My experience with btrfs is quite old now, but I remember being plauged with enospc errors requiring a lot of balancing to correct.
I have been running zfs for a decade or so now on a 6 disk array and the only issue I have had was the pool not being imported on boot sometimes but that seems fixed now. I recenty replaced 2 disks in that array and the whole replace / rebuild process went quite well. I felt confident there would be no uncorrectable read errors during the rebuild because the monthly scrub had recently run. Overall I’m quite impressed with zfs.
All that said I would never run a root filesystem with an out of tree kernel module. So I’m still using xfs on /