Assistant, as folks with Android phones already know, is much smarter than Siri. You can use it to ask you how to say something in another language, to play music through most music apps (not just Apple Music), to play movies on your TV's Chromecast and more. Also, unlike Siri, you can even type in your queries, in case you don't want to speak out in public.
Google Assistant is great, but there's still one function where Siri wins: You can't simply say "Ok Google" to open it. Instead, you'll need to manually launch the app each time you want to run it. That may make it hard for Google to convert iPhone users over, even if it is better.
Let's take a look at some of the many functions you can do already. Keep in mind that many more, including the ability to identify objects spotted by your camera, will launch in the coming months.