Loup Ventures:

We recently tested four smart speakers by asking Alexa, Siri, Google Assistant, and Cortana 800 questions each. Google Assistant was able to answer 88% of them correctly vs. Siri at 75%, Alexa at 73%, and Cortana at 63%. Last year, Google Assistant was able to answer 81% correctly vs. Siri (Feb-18) at 52%, Alexa at 64%, and Cortana at 56%.

Interesting that all four smart speaker systems got smarter over time.