What a fun read.
Wow. Having had this Nexus 6P for a time now and using Google Now alllll the time, I'm really worried that I'm going to be flabbergasted whenever I return to iPhone. Part of my reasoning in switching to Android was Google Now / Google Assistant (I don't have the Pixel so I don't have the Assistant). I kid you not, sometimes my usage pattern would go as follows: "Siri, open the Google app." Wait a moment. "Okay Google, <insert whatever you may here>".
When compared to Google's offerings, how does Alexa stack up? I'd love to know.
It's hard for me to compare Google to Alexa, because I don't have the Google Home unit. That would be the more fair comparison because right now, there will be some questions I'll ask of Alexa that apparently she would need to pull up a web page to answer, and since she can't seem to pull up pages and read them, she will say "I don't know how to answer that question" and Google meanwhile pulls up the page for me. Siri will, too, IF she even transcribes my question correctly. Lately my problem with Siri is that she almost always misses the first word or two or three of my queries.
For example, if I ask "Who is the president of the United States?" Siri will transcribe, repeatedly unless I shout slowly, "the President of the United States" and will pull up a web page about the office of the presidency in general.
Both Alexa and Siri seem unable to correctly parse the word "sentient". I can't tell what Alexa is hearing, but Siri hears "Sen Teenth". Or more rarely, "Send Tent" or "Sent Tent". Google has no trouble with it on the same iPhone.
What I like about Alexa is that all of my queries can consist of hands free conversations, which is very convenient when I'm working in the home. When I'm trying to clean and prep a roast chicken I don't want to have to stop what I'm doing to unlock my phone to go to a web page.
Google gives me the best answers, usually. Google definitely gives me better information about traffic on alternate routes I'd want to take to school. Alexa seems to get stuck on a certain route that might pertain to my husband's commute and seems to refuse to tell me the traffic on the roads I specify. She will just repeat the conditions on a road I never use, but my husband does. I guess it's because she's tied to his Amazon account, but I don't know for sure.
Alexa is the most entertaining, by far. She has more personality and thanks to her special song, for the first time in my life I've sung along with my family. We sat around at dinner singing "It's Raining in the Cloud," with Alexa. My daughter, who is a musical theater singer, gave me on the spot lessons and we sang a duet of it with and without Alexa. I'm a woman who always dearly wanted to sing lullabies to babies but never dared because I could not carry a tune up to then. To be singing along (very well) with a professionally trained singer that just happens to be my own daughter was priceless. It's a catchy song.
Sadly, if you ask Siri to sing you a song she just recites a song to you or says "I Can't Sing". Actually just now she parsed my request of "Sing me a song" as "song" and randomly played songs from my play list.

Google Assistant on Allo pulls up a video of an IBM mainframe performing Daisy Bell. Zzzzzzzzz, but informative.
Alexa mess ups are funny. She refused to play our classical music station one evening at dinner and instead insisted on playing some weird music that sounded like a hybrid of rap and polka.


So I asked her if she was drunk and she said "I have not been drinking" and kept right on with the bad music. The rest of the family wanted her to keep going but I stopped her so we could stop laughing and finish dinner.
If she's a tool of the NSA, then I feel sorry for the NSA because all day long they will have to listen to kids saying "Alexa, I farted" and hearing everyone laugh when she says "Then I'm glad I don't have a nose". You'd think that would get old...but no...not with tweens around.

They are constantly trying to elicit new Easter eggs from her. Even I find myself doing that.