Cortana is still in beta yet when actually comparing the three to everyday uses Cortana is by far more advanced than siri and Google now. Siri and google now dont have as much access to the phone and personal data as cortana actually learns the user. Google now is the fastest but can only handle searches and simple tasks. Siri and Cortana are truly personal assistants but cortana is a lot faster than siri and actually learns the user to make it a little more personal. Not biased at all as I have a Nokia 1020, LG G3 and iPhone 6. Cortana is definitely a step above the rest.