something to keep in mind with Google Now, is that it isn't aimed at being a personal assistant in your phone, but does allow for limited functionality like setting appointments, and that sort of thing. it's meant to get information to you. Siri is aimed at being a personal assistant, part of which includes giving you information you ask it for.
so it's only natural that Google smokes Siri at retrieving information from the web, whereas Siri probably has a bigger number of actions/tasks it can perform for you. (for now)
i think Google will position Now like that for a while and continue improving and speeding up how it works before adding in more personal assistant features. this is a HUGE first step- especially for being a x.1 release over ICS. just imagine what they'll do with 4.2 or 4.3...