It's more natural as in you can say "What's the weather like today?" or "Will I need an umbrella today?", compared to voice control where you would only be able to say "Tell me the weather.". That may be a bad example, but voice control type services you have a predetermined list of things you can say and if you change one word it doesn't know what to do. Siri figures out what you are talking about and responds correctly (for what it can answer).