It doesn't really matter, in my opinion, because the major learning hurdle generally isn't the languages, it's the Cocoa frameworks. Experienced programmers can

It doesn't really matter, in my opinion, because the major learning hurdle generally isn't the languages, it's the Cocoa frameworks. Experienced programmers can pick up Swift or Obj-C in 2-3 days. The frameworks will take you considerably longer to feel comfortable with. That said, Swift isn't production-ready yet, and there's not a wealth of books and documentation, but it's very, very likely the future of iOS and OS X application development.