When comparing GNU/FreeBSD vs NetBSD, the Slant community recommends NetBSD for most people. In the question“What are the best server OSes?” NetBSD is ranked 5th while GNU/FreeBSD is ranked 9th. The most important reason people chose NetBSD is:
It adheres to traditional Unix and new defined standards.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Very customizable
It's more barebones than Linux so you can customize it every way you like.
Pro Not tied to systemd
Pro Clean design
Clang toolchain has a cleaner design than gcc, it's easier to implement a front-end to LLVM.
Pro Adhere to the standard
It adheres to traditional Unix and new defined standards.
Pro It's Open Source
It's open source with a BSD License, which is much more business friendly than GPL. It's the real ancestor of Mac, that is being used nowadays.
Pro It's real
Under NetBSD csh is csh not tcsh; also vi is real vi not elvis, nvi or vim. It's ideal for purists.
Pro Architecture portability
It's the most portable OS in the world when considering what architectures it can run on. It runs on very wide range of hardware, from toaster to satellites. This of course does not mean it supports drivers for many consumer facing products making it a difficult solution to just boot up and use when compared to other OSs.
Pro Clean source code
It prioritizes source code cleanliness over anything.
Cons
Con Linux can do pretty much everything it can, and better
Unless you're looking for some niche server functionality, it's pretty much certain that a linux distro already has whatever you want in a more efficient and easier to use form.
Con Server-oriented, good for developing back-end software and not much else
Con No systemd
Systemd makes it trivial to automatically start and manage programs, offering a whole lot more control than a cobbled together bundle of some archaic init system, cron and random bash scripts.
Con Lack of drivers
It lacks drivers for some new devices.