I figured out a couple things today in talking to the folks at T-Mobile today.
AT&T charges $39.99 for 450 minutes a month. $4.99 more gets you 200 SMS messages.
T-Mobile charges $39.99 for 600 minutes a month. $4.99 more gets you 400 messages.
However, your minutes roll over at AT&T and you can call any other AT&T customer for free all the time.
At T-Mobile, you have to add M2M service for $6.99 a month in order to call other T customers for “free.” And there’s no rollover.
T-Mobile is a better deal, dollar-for-dollar. The question (and real value) if you’re using AT&T is getting all you can out of rollover minutes, and calling your other AT&T peeps for free. With more customers than any other carrier in the U.S., AT&T probably has more of your friends on their network than any other carrier.