I partially disagree with the claim that ZFS is slower than ext4/xfs. It is, but only as long as you don't use ext4/xfs on top of LVM to get similar snapshot capabilities etc. Then ZFS starts to win.

So if you only need a plain filesystem, ext4/xfs are great and you will get better performance.

If you need/want snapshots, e.g. to do backups that way, it makes sense to look at ZFS.