We have an Echo device as well, and the difference between it's performance and Siri's is huge. Alexa is easily 10x the voice assistance that Siri is.
But people underestimate how frequently Alexa is listening to what's happening in your home. Alexa is always listening, so long as it's plugged in.
Let me give you an example: I asked Alexa to play "We Will Rock You" by Queen, it provided a newer remix I wasn't interested in. I tried again, being more specific, and it still played the newer remix. I then told it to stop, and used Hey Siri. I only have the old version in my iTunes, so Siri couldn't fail to get it right.
So far so good.
But when I asked Alexa to play that song again later on in the day, without specifying the version, it then played the one Siri had. Quite simply it had listened while i was using another device and adapted its response.
Yes that's an improved user experience, but the eavesdropping is concerning.
In the small print for Alexa's terms and conditions, you agree to it "listening" at other times to improve its performance. This improvement includes sample recordings being listened to by staff at Amazon to see if their program is understanding you correctly. All of which is a sophisticated way of saying that things said in your home, when you're not using Alexa, are recorded by that device and sent to staff at Amazon listened to to check if their devices have recorded it correctly. It's not everything you say, of course, but you never know when the sample is being taken.
I'm not always happy with that. But most of the time it's a tolerable compromise for the improved performance. But I do pull the plug on it if I want to talk about certain subjects.