Beyond getting support for devices completely absent on freebsd, quality of drivers, bugs much more rapidly squashed, and general misc features absent on the bsd side like NBASE-T.
Virtualization means you now have multiple layers of drivers and privileged code in the mix to add and amplify bugs, it can and should work but if you are doing this in the name of stability that is a bit curious.
The reason Netflix can do what they do is they have good relationship with their HW vendors, NVIDIA(Mellanox) and Chelsio. If they were on Linux, they'd need the same level of support.
I use Linux for my router now because my server is NixOS, so I was able to consolidate my router into my server and turn off a machine (and thus save a little power), and I have so thoroughly drunk the Kool-aid for NixOS that I kind of want to put it everywhere. I run the latest kernel and I update daily, so I think most bugfixes (and hopefully security updates) will manifest quick enough.