Which of the three would work best in the SF Bay Area on AT&T

Column 2, if you like HD Voice and it's compatible with AT&T's HD Voice.

The question is whether AT&T provides good signal where you need signal. A great signal in the hallway outside your office, but a dead spot in almost the entire office (you'd be surprised) means that you can't use your phone while you're sitting at your desk, and you won't hear any incoming calls. "But the rest of the building has solid coverage." That still doesn't give you a signal where you need one. The same thing with a dead spot right around your chair in your den - you have to leave your phone on the other side of the room. (I've seen them as small as 8" diameter circles about 1" thick and as large as a suburban house. And back in the day, Nextel skipped over an entire village. Even today, in one - call it "poor town" - around here, there's almost no AT&T signal. A spot here, a spot here, but no one there can afford AT&T so they won't set up even a small cell or two. TMobile, due to the location of their tower [I'm sure it's just coincidence] covers the town like a blanket.)
 
I completely agree that good coverage is the important issue. When I visit some places, like my mom's apartment in San Mateo I can barely get internet access, while most places in the Bay Area are fine. Walking down the entrance hall everything comes in fine but in her apartment reception drops significantly. It is a location problem.

But is it also a band channel problem? I list the three columns to compare the different bands that the three different phones cover. Each of the three columns has a different set of UMTS, LTE(FDD) and LTE(TDD) bands. Makes me think that one of the three columns might be theoretically better suited to AT&T while a different one might be better suited to Verizon. I am on my bro's AT&T family plan so I want to pick a phone with theoretically the fullest use of the band's coverage for AT&T.
 
Column 1 = Moto Z3 Play
Column 2 = Samsung Galaxy S8+
Column 3 = Huawei Mate 10 Pro

I'm assuming all will work about the same on ATT network.

How about Pixel 2XL?