If you don't have any experience, then probably FreeBSD imho; Follows unix philosophy, stable, built-in support for ZFS, dns caching, NFSv3 & NFSv4, used as the base system for stuff like OPNsense, freenas and a bunch of other stuff at one point in time or another.
And it's really well documented.
If you already have a set of linux utilities or a certain distro you really like then go for that. But it's almost always going to mix-up user and system installations along with needing to learn new stuff for every distro and hoping it's stable with all the different package managers you will need.
If you don't have any experience, then probably FreeBSD imho; Follows unix philosophy, stable, built-in support for ZFS, dns caching, NFSv3 & NFSv4, used as the base system for stuff like OPNsense, freenas and a bunch of other stuff at one point in time or another.
And it's really well documented.
If you already have a set of linux utilities or a certain distro you really like then go for that. But it's almost always going to mix-up user and system installations along with needing to learn new stuff for every distro and hoping it's stable with all the different package managers you will need.