I think our dear FreeBSD project lacks on some "branding" of technologies thus people don't understand why they can use FreeBSD instead of GNU.
For now ZFS can be subtractable from advantages of FreeBSD because de-facto it's one another Linux future ported to FreeBSD.
FreeBSD is very comfortable to keep in control all of system, but "on paper" it seems like FreeBSD is a layer (say linuxkpi) for GNU/Linux, so people think "why don't just use GNU/Linux?"
For example on Wikipedia OpenBSD has a lot of homegrown projects and pros at all. FreeBSD seems doesn't have so "marketing stuffing".