Two tiers very evident in US telco rankings

OpenSignal has released some more granular insight on the performance of the top four telcos in the US and it is very clear there are two tiers; Verizon and T-Mobile US are best-in-breed, AT&T and Sprint are not.
When the firm released its State of Mobile Networks in the US report T-Mobile US was recognised as the leader for pretty much everything, but when you look deeper into the statistics in the individual regions, the competition is a lot closer than top-line figures would suggest. Veri