Type hinting v duck typing

Using the following simple Example (coded in php):

public function doSomething(Registry $registry)
{
    $object = $registry->getData('object_key');
    if ($object) {
        //use the object to do something
    }
}

public function doSomething($registry)
{
    $object = $registry->getData('object_key');
    if ($object) {
        //use the object to do something
    }
}

What are the benefits of either approach?

Both will ultimately fail just at different points:

The first example will fail if an object not of type Registry is passed, and the second will fail if the object passed does not implement a getData method.

How do you choose when to use either approach?