Siri is probably the dumbest assistant today but its (her?) UX has improved considerably much faster than the others.

Siri stopped needless chatter several major iOS updates ago - albeit mostly by hardcoding what to show as a sort of mini in-Siri widget instead of repeating what you just told it and asking for confirmation.

Now, if I ask Siri to set an alarm for 7am instead of “Ok <butchered pronunciation of my name>, I have set your seven o’clock alarm for tomorrow morning” I just see a blink (and haptic feedback?) then a widget showing me an alarm bubble with the date and time and a on/off toggle (set to on) that I can clock to undo.

Of course, Siri has the benefit of being a mixed medium “intelligence,” it can use the screen and the audio/mic.