In terms of native voice assistant software on mobile devices, we have Siri, Google Now, and Cortana which are made by Apple, Google, and Microsoft respectively. They all have their strong traits and also their fair share of weaknesses, but speaking overall, is there one that does better than the rest?
According to a recent study conducted by Experts Exchange, they pit all three voice assistants against each other and based on their findings, it seems that Siri has (surprisingly) pulled ahead of the competition. Having used both Siri and Google Now, I have personally found Siri to be less accurate and intuitive compared to Google Now, which is why these results are a bit surprising, but your experience might be different.
The result of the study found that in terms of performing as intended and user satisfaction, Siri for the most part performed the best, with Google Now coming in second place, and Cortana trailing behind in third. They also found that the percent of incorrect answers was at 2.6% for Siri, 4% for Google Now, and 8% for Cortana.
They also found that in terms of being able to deliver an answer without pointing users to a web search, both Siri and Google Now tied at 5% while Cortana was at 7%. That being said we suppose at the end of the day your experience will vary depending on what you really need to do with your phone, but for now at least as far as this study is concerned, Siri is the clear winner.