Seconding this. I never used Siri because it required holding the phone up to my face for reliable results. The Echo Dot can hear me across the room even as its playing music and other people are talking. The Fire tablets have Alexa built in but I believe they not only require a button-push to activate, but rely on their limited mics.

Until Alexa, I hadn't tried Siri since its initial launch years ago. I was surprised to see that its AI/NLP was as good as Alexa's. So the killer feature really is the convenient and reliable interface provided by the Echo's mics.

one day there will be a cheap bluetooth mic array that works with anything. I'm surprised that day hasn't arrived yet