The feeling I’ve heard from people is Alexa was way better than Siri at first.

Over time Siri got better. Not great but better. Alexa had mostly stayed the same or perhaps gotten a touch worse except for adding ads and other annoyances.

I’ve never used anything but Siri. It works decently, definitely has its moods/dumb-as-a-post moments. But I’ve learn what works well and for that it’s proven very useful.