A good reason for using btrfs over zfs is that btrfs is available by default on the Linux kernel, while zfs is only available as a third-party out-of-tree modul

A good reason for using btrfs over zfs is that btrfs is available by default on the Linux kernel, while zfs is only available as a third-party out-of-tree module, with all the usual problems out-of-tree modules have.