Siri has gotten a little better, but don't try to compare it to Google Now. That's just crazy.
I don't really agree with this. They have their strengths. Google Now works best for the things Google is traditionally good at - web lookup-type searches using simple terms.
Siri has much better integration with the operating system itself than Google Now (and I'm comparing Google Now on Android to Siri on iOS, since it's not a fair fight otherwise.) Google Now lets you perform some OS-related functions, but Siri supports a lot more and with more flexibility. For instance, both services allow you to launch apps by name, but Siri as far better at it - it always gets the right app, even if the name is complex or I have similarly named app or I don't speak the name exactly as the app is titled. It virtually never fails to open the right thing. Google Now on my Nexus 5 requires me to get the app's name perfect every time, and even then will randomly decide to do a web search for the term instead, even if what I said exactly matches an installed app. It also has trouble with things like numbers in names – it always seems to interpret the spoken number as the word (e.g., "one" inside of "1") and when it does so it will refuse to open any apps that have the number written as a digit (until recently this consistently did not work. They seem to have made some back end changes and it will now sometimes do digit-to-word mapping correctly, but it seems very random and unreliable still.)
Siri's natural language parsing is also much better (as imperfect as it can be at times.) For instance, if I ask Siri "What's the highest rated restaurant in town?" it will leverage Yelp and bring up the profile for the highest rated restaurant, along with reviews, hours, directions, menus, etc. If I ask Google Now the same question, it just does a standard Google search for that exact phrase.
Google Now's killer feature seems to be its automatic component - the ability to use your search history, location history and email to display cards with timely and relevant data. Unfortunately in my experience about 95% of the utility of this feature comes from the email scanning, which requires a consumer gmail account in order to work. Even my Google Apps for Business account is not compatible. If you aren't using free Gmail as your only email account, this feature isn't very useful at all.