I would recommend Obj-C, of course.
— native application, the UI elements work exactly as the user expects;
— no unnecessary layers of abstraction, the code is faster (comparing with phonegap significantly);
— complete superset of the C language, a lot of reusable source code;
— Xcode IDE, particularly the debugging/profiling on both the emulator and on the device;
— OpenGL ES, you can make fast three-dimensional toys (particularly ported quake3 engine, Unreal Engine commercial).