Отдельные раскадровки для iPhone 5 и iPhone 4S

В вашем делегате приложения вам нужно будет добавить/заменить следующий код в - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

CGRect screenBounds = [[UIScreen mainScreen] bounds];
if (screenBounds.size.height == 568) {
    self.viewController = [[ViewController alloc] initWithNibName:@"ViewController_4inch" bundle:nil];
} else {
    self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
}

где ViewController_4inch — имя nib-файла, предназначенного для экрана iPhone 5.

ОБНОВЛЕНИЕ (ОТВЕТ ДЛЯ КОНКРЕТНОЙ РАССКАЗКИ):

Чтобы загрузить разные раскадровки при запуске, используйте этот код:

    CGSize iOSDeviceScreenSize = [[UIScreen mainScreen] bounds].size;

    if (iOSDeviceScreenSize.height == 480)
    {   
        // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone35
        UIStoryboard *iPhone35Storyboard = [UIStoryboard storyboardWithName:@"Storyboard_iPhone35" bundle:nil];

        // Instantiate the initial view controller object from the storyboard
        UIViewController *initialViewController = [iPhone35Storyboard instantiateInitialViewController];

        // Instantiate a UIWindow object and initialize it with the screen size of the iOS device
        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

        // Set the initial view controller to be the root view controller of the window object
        self.window.rootViewController  = initialViewController;

        // Set the window object to be the key window and show it
        [self.window makeKeyAndVisible];
    }

    if (iOSDeviceScreenSize.height == 568)
    {   // iPhone 5 and iPod Touch 5th generation: 4 inch screen
        // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone4
        UIStoryboard *iPhone4Storyboard = [UIStoryboard storyboardWithName:@"Storyboard_iPhone4" bundle:nil];

        UIViewController *initialViewController = [iPhone4Storyboard instantiateInitialViewController];
        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
        self.window.rootViewController  = initialViewController;
        [self.window makeKeyAndVisible];
    }