To be fair, Google Assistant started out better but now has just been neglected and actively undermined and had features taken away. My understanding is the whole team was folded into Gemini and it's a classic "old thing deprecated new thing not ready yet"
I don't do the Amazon ecosystem so can't say about Alexa.
There was a period where Google Assistant was so useful. Could control phone functions, set events, reminders, alarms, change volume, reliabily message someone. It's wild to think through all the things it used to do well that it simply cannot do today.
Alexa has dropped off. Every echo device I have was better in the past. My wife is lucky to trigger them half the time. They have always done better with male voices, but it’s worse than ever. And when Alexa does respond, it’s frequently an ad.
Of course, the division famously lost $10bn, and so they must be reducing compute. But the fall has been noticeable.
When I ask it to read me the last text message from Person X, it says that this feature is no longer available.
When I switch the Assistant to Gemini, and ask it to read me the last text message from Person X, it says it doesn't have access to my text messages. When pressed for an explanation, it gives me a long winded excuse that having access to my text messages would be a serious privacy violation. Absolute nonsense.
I don't do the Amazon ecosystem so can't say about Alexa.