Actually, Alexa is much less powerful than Siri. She can speak many fewer languages and, as this test and others show, when it comes to integration with your key items like your phone and commands, Alexa is left in the dust. Don't confuse the hype you hear about Alexa "skills." Surveys show that most people don't even activate or use even one of the 4000 skills. Yes, she can "fart on command," but EVERY survey shows that Siri already does what the vast majority of smart phones/speakers want their digital assistant to do- control Homekit stuff, get you directions, read messages, check on traffic, play music/podcasts, set reminders/alarms, control features on your phone, answer basic questions, do math, etc. Sir works great in the car, with the TV, etc.
And there's even bigger, equally meaningless hype about putting Alexa into things like your refrigerator and toaster. This is all a gimmick that manufacturers are shoving into things but people don't care about, like 3D TV. They are now advertising a toilet with Alexa built in, but I don't recall the huge clamor from people wanting to have Amazon control their flushes. Also, people may later regret as Amazon has much less security built in, and voice controlled switches is another point of failure. Apple has no intention of playing in that silly arena.
https://www.usatoday.com/story/tech/2018/01/11/do-we-really-need-alexa-powered-toilet/1024646001/