In my experince, bsd in years ahead of linux, especially on highly loaded servers.
In the past, I had situations where linux server where on their knees, while bsd could still manage to give me a login shell.

I know that since, linux kernel have had a major rewrite, and it seems to have brought it near bsd, but still bsd seems to have the winning hand.

So, for a workstation or a "casual" server, I'd say that linux is the path to go, but on a highly critical server, which will be massively accessed, I'd recommand BSD over linux.