Right now, OSX has become increasingly hostile to dev and Linux is great at modularizing other features FreeBSD built years ago.
Lately I've been trying to ship software from the newly open sourced and open-er licensed .NET CoreCLR and Mono (via C# & F# respectively) and FreeBSD. The results are surprisingly good, especially with the new native executable compilation target stuff.
And the docker pass-through to FreeBSD jails is hot like the sun. It's like a Docker container with similar constraints but without such severe security issues. That and the new network stack makes containers on FreeBSD pretty compelling, even compared to the 1.9 security work.
And there is that thing where linux is locked in a death roll with itself regarding its initalization system? Freebsd don't have that. And that thing where Apple makes you boot into safe mode and flip an NVRAM bit to actually have root on your box?
Of course, I'm not personally shipping code on iOS, so this discussion is a lot more flexible for me than it might be for many.