I think Legacy AT&T made the wrong choices in divesture - they should have held on to WECo (and the labs) and the local BOC's - and spun off Long Lines - I dont know how they would have worked culturally though (or if it would have passed DOJ muster) because Long Lines was part of the core identity of AT&T.
You measure by market cap. Acquisitions are paid in money, not subscribers.
Edit: Also wikipedia says that the AT&T stat includes "connected devices". If that really means they count all individual connected devices, thats a useless comparison. One customer can have multiple devices.
ATT spends its money paying for debt used to buy DirecTV and Time Warner at obscene prices, even though anyone with half a brain cell would have known those were legacy businesses were on their way out.