I've been using Siri for years, even before it was purchased by Apple (AAPL) and incorporated into the company's mobile operating system, iOS. When Siri was an independent product, it was a fun curiosity, capable of doing clever things like looking up dining options and buying you tickets for movie showings at nearby theaters. Then it arrived in iOS and Apple gutted the service, removing many its most compelling features.
Since that time, Apple has restored Siri and even improved on it significantly. That's good, because it's no longer the only personal assistant around. Google Now delivers substantially the same experience to Android users, and Microsoft has finally released Cortana, its Halo-themed voice assistant, for Windows Phone 8.1.
The logical question: How do these three similar services compare?
For the most part, the good news is that no matter whether you use iPhone, Android or Windows Phone, you're guaranteed a similar general experience. If you were worried, for example, that Cortana would ship as a typical Microsoft 1.0 product -- weak, buggy and underpowered -- you'll be pleased to know that its capabilities are roughly analogous to both Siri and Google Now even in its early state. Gizmodo recently performed an excellent side-by-side comparison, and the video shows that all three services delivered substantially the same experience. By and large, they're on equal footing.
Siri is the elder statesman of voice assistants, and any comparison necessarily must treat Apple's assistant as a baseline for comparison. Not only is Siri able to smartly find information online, it can trigger actions on the phone itself (like start a timer, send messages and toggle through features like Wi-Fi and Bluetooth). Siri can do ordinary Web searches, book reservations and even reference tools like Wolfram Alpha for deeper research. And if you want to teach Siri to do more, such as have the ability to control home-automation devices like the Nest thermostat, for example, you might consider trying GoogolPlex, which routes your commands to a proxy server for additional processing.
Google Now is Android's answer to Siri, and it does most of the same stuff. Where Google Now shines is in its ability to be a predictive personal assistant. Siri only does what she's told, when she's told to do it. Google Now is all about getting in front of your daily schedule, problems and interests via Google's card-based interface.
By giving Google Now access to the details of your life, such as the contents of your emails, Google Now automatically advises you about your daily commute time, flight status and delays when you travel, and much more. And Google Now has one key feature you won't find in either Cortana or Siri: On select Android handsets, you can talk to Google Now completely hands-free without touching the phone at all.
In that sense, it's easy to get the impression that Cortana is trying to emulate Google. Cortana wants to integrate itself into your life deeply by accessing email, contacts and social media. After that, though, the service uses a card-like mechanism to offer information it thinks you'll like before you think to ask for it. It's still young, though, and doesn't appear to be nearly as helpful as Google Now. It doesn't yet think you care about your commute time, for example, and it misses opportunities to proactively advise you about flight status when you travel. But the system is smart enough to understand the context of email, and has helpful features like making it easy to schedule meetings based on key pieces of information in the message.
Of course, all three voice assistants are in a nearly constant cycle of development updates, and improvements. Each will get better, and it's not unreasonable to expect that they'll all converge on a similar set of skills in the future.