Google also does a great job of combing through your email and location, suggesting places to go and setting reminders of upcoming events. One of Google Now's claims to fame is mining your email and your calendar for your next appointment, determining when it is, checking traffic, and calculating when you need to leave. That's integration.
I would appreciate seeing a bit more information about my current location, though, possibly culling some of Google's Field Trip app knowledge into a better contextual awareness.
Google Now also now ties into your desktop PC. If you don't notice your phone's vibration in your pocket, a notice will pop up in the corner of your Chrome browser.
This isn't the final word on the subject; all three services will continue to evolve, and improve. And all three have unique talents, providing intriguing directions for differentiation. For now, Google Now sets the bar for what a digital assistant should be, and based on our tests, it's still the superior service. Microsoft's Cortana makes a valiant effort, but it needs to shore up some of its weaknesses, such as Facebook and Twitter integration. And quite frankly, if Apple built in some predictive capabilities into Siri, Siri could retake the lead.
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