I have been a huge ZFS fan since the Solaris days and have had a bad experience with btrfs, yet I’d be remiss if I didn’t point out that (the last time I dove into it) the btrfs for Windows project was in a better and more useable shape than the ZFS for Windows one.
I still dream that this will one day be useable. ReFS has a few interesting ZFS ideas, Windows Storage Spaces incorporates yet some more, but fails to do so in a way that actually gives the sysadmin any confidence or visibility into the underlying layout and misses out on a whole lot of zpool goodness.