Consumer Reports’s rankings, which put AT&T last and Verizon first, were based on actual customer surveys. Actual customers reporting their actual experiences.
Consumer Reports takes no advertising for any of their publications. Paying subscribers supports their efforts. Perhaps if they had an army of volunteers willing to purchase products, test equipment, etc. they could offer all their content for free.
Too bad Consumer Reports is still one of the few print sources with a pay wall. It would be interesting to see the results for other cities.