I wouldn't use either of them.
You only have to spend a few minutes poking around any of these corporations' custom Linux distros to see they are almost universally fucking awful. Consider, Synology ship many of their NAS type devices with BTRFS as the default/only option, as if that were a perfectly reasonable thing to do. And QNAP's engineers might be dangerously overconfident in their understanding of ZFS, implementing basic features in ways that seem more cargo-cult driven than informed by actual ZFS mechanics—and as if that isn't enough, recklessly extending it at a low level while continuing to call it ZFS because who wouldn't want to ride those coattails?
I suppose this is probably obvious, but I believe meaningful quality and capitalism are fundamentally incompatible—especially security, as in the real (i.e. non-theatre) version, because it tends to be obnoxious when done correctly, and the moment the marketing department gets to veto boring nerd shit, well, good luck. Just look at the so-called enterprise network security vendors like Fortinet and SonicWall, it's honestly mind-blowing what they get away with.