People love to rag on Siri because it's an easy target. In no way is it terrible, but a lot of people think it should be much better due to it's time on the market and Apple's software prowess. At least it's not as bad as Bixby.

Each assistant has it's strengths and weaknesses. MKBHD recently did a voice assistant challenge. Of note: you can tell where he was trying to "help" certain assistants in some queries - especially his speech pace with Bixby. To be fair, it's new on block.
I see why he chose the phones in question- but was he afraid to add Cortana to the mix too? Granted, only the HP Elite X3 and Alcatel 4S and some older Lumia's are available for Windows 10 now but even so...
I tried the experiment out myself with Cortana and it did pretty good.
I tried to do some extra stuff with Cortana on a 950XL to see how it coped so I said:
'Send a Message to my wife'
I got the reply - OK - who are you sending the message to'
I said the name of the person in my address book.
I got the reply - OK - do you want me to associate 'name of person' as your wife?
'Yes'
'OK - what is your message'
'Hi there. Just a quick message to tell you that I'm running late and will be home around 5:30pm'
'Alright <she then repeats message> then adds 'Send it, add more or start again'
'Send it'
'OK - Message sent'.
All worked seamlessly. I then tried
'Add a message to my calendar for tomorrow at 2:30pm called 'Design Meeting' for 90 mins.
'Alright - repeats everything back, getting the 90 minutes correct i.e. 2:30-4pm and not 'Design Meeting for 90 mins'.
Is this correct?
Yes
OK
Next - Translate 'What's the quickest way to the railway station' into Japanese.
Sure things - here is how to say 'repeats question' into Japanese. A Japanese speaker then speaks and the kanji appears on screen.
and so on... how does Siri / Bixby / Google deal with all this?