AT&T (NYSE: T) might not be the biggest wireless carrier in subscribers anymore, but it is the leader in smartphone users. The carrier captured twice as many smartphones than any other U.S. carrier, AT&T announced today based on comScore’s research. According to comScore’s M:Metrics, A&T had 11.8 million smartphone customers in March, more than double the 5.1 million customers of the combined Verizon (NYSE: VZ) and Alltel and totaling 47% of all U.S. smartphone customers. Sprint (NYSE: S) and T-Mobile (NYSE: DT) trailed the top two with 4 and 3.7 million smartphone users, respectively. more