While they do share the same code base, personally (and therefore anecdotally) I have noticed an issue where on Linux with ZFS my programs will get OOM killed whereas they won't on FreeBSD+ZFS or on Linux+ext4. My theory was that the ARC pages on Linux weren't available for clearing under memory pressure whereas maybe they were in FreeBSD but that's just a guess. Hopefully someone knows more, but at least anecdotally even with the "same" ZFS code base, they can perform differently in situ.