It is easy, Brownlee is primary mac/iphone user BUT he builds his channel on bashing apple, majority of his followers are android users and fanboys that aporeciate his ironic comments about apple products.This comes across to me as though Marques uses Android as his daily phone and knows what to expect from it and hopes that Siri will give him the same result, and not the other way around. For example, he either doesn't know or purposefully omitted that you can ask Siri for "my pictures of cats" and she will show you your own pictures of cats, rather than generic pictures of cats.
He also persisted on asking a contextual follow up question when Siri clearly missed the original question. Of course she's not going to know the follow up. For the record, she understood the same exact question when I asked "How tall is Barack Obama" and unlimited follow ups like "where was he born", "how old is he", etc etc etc... Siri also understood "Mark Zuckerberg" the first time I asked.
I was impressed that Siri was consistently faster at answering questions than Google Assistant and I appreciated the presentation of the answers in a well designed card instead of the small busy copy in Google's responses.
Finally, another one of his criticisms was that Siri presents visual information rather than read it out. Again, his ignorance of iOS is showing. Siri will read information to you when she thinks that you're doing an activity where you're not looking at the screen. For example, when summoning Siri with "Hey Siri", she will read you the answer. If you call her up by pressing the headphone mic button, she'll present information audibly. But when you're pressing the home button to bring up Siri, she correctly assumes that you have the iPhone in front of you and gives you visual information.
Either Brownlee is showing favouritism in his comparisons or he needs to learn more about iOS if he wants to remain credible.
So, if he makes any comparison, I believe it is at least little bid biased (in a sense: lets show anything for which I can say apple is worse - this makes majority of his followers happy and his channel generating revenue).
To the topic, dont know about goigle assisstant but here in my country, siri is unusable - does not speak my language, does not have contextual info (and does not understand perfectly my english with my broken accent