NetBSD hands down the most fuss-free OS for webserver things I have ever used. Not once have system updates ever broken my server. It "just worx" and you don't have to fiddle with things once set up.

OpenBSD is great for security minded things - it can be a bit finicky when trying to build things you'd use on a normal daily driver (which is why I still Gentoo and build own kernels) but it seems to get more usable with each release.