I've used both Btrfs and Zfs as Linux root filesystems and at the time I tested (about 4-5 years ago) Btrfs had much worse performance. I've heard that Btrfs greatly improved performance on recent kernels though.
What bothers me about Zfs is that it uses a different caching mechanism (ARC) than Linux page cache. With ARC you actually see the memory used in tools like htop and gnome system monitor (it is not cool seeing half your memory being used when no programs are running). ARC is supposed to release memory when needed (never tested though), so it might not be an issue.
After about an year of playing with both filesystems on my Linux laptop, I decided the checksumming is not worth the performance loss and switched back to ext4, which is significantly faster than both filesystems. Still use ZFS on backup drives for checksumming data at rest and easy incremental replication with `zfs send`.
My main problem with ZFS is the very limited number of ways you can change your setup. No removing drives, no shrinking, etc. Probably fine for (bare-metal) production systems, but not so friendly with desktops/laptops, where I would still love to have snapshots and send-recv support.
What bothers me about Zfs is that it uses a different caching mechanism (ARC) than Linux page cache. With ARC you actually see the memory used in tools like htop and gnome system monitor (it is not cool seeing half your memory being used when no programs are running). ARC is supposed to release memory when needed (never tested though), so it might not be an issue.
After about an year of playing with both filesystems on my Linux laptop, I decided the checksumming is not worth the performance loss and switched back to ext4, which is significantly faster than both filesystems. Still use ZFS on backup drives for checksumming data at rest and easy incremental replication with `zfs send`.