I’ve been running ZFS in the form of FreeNAS/TrueNAS in production environments for the past 12 years or so. Started with around 5TB and currently have nearly 300TB across several servers. Mostly NFS nowadays, but have shared out SMB and iSCSI.
No data loss. Drives have been easy to replace and re-silver. We have had a couple instances where a failing ZIL or L2ARC has crashed a storage server and taken storage offline, but removing/replacing the log device got us up and running without data loss.
Btrfs I only have experience on home systems. It has reliably stored my data for several years now, but I’m about to put it to the test this weekend. I plan on adding 4x8TB disks to a 4TB mirror to turn it into a 20TB RAID10. Wish me luck!