The key difference between Siri and Watson from a user perspective is essentially the level of complexity and intelligence. Watson could probably do the search

The key difference between Siri and Watson from a user perspective is essentially the level of complexity and intelligence. Watson could probably do the searches that Siri does already (though does not yet have a voice interface - does NPL with text only so far) but its main objective is to solve very complicated problems. It is currently "in Medical School," for example, to absorb everything we know in text and experiential formats about cancer. Much harder than finding me the nearest parking garage.