Shure Beta 58A vs Shure SM58
The Beta 58A is the evolution of the SM58: still a handheld dynamic vocal mic, but with a different polar pattern and magnet.
Which one to choose
The Beta 58A is supercardioid with a neodymium magnet: more output, more high-end presence and better side rejection on loud stages. In return it picks up a little from behind, so wedges go at an angle rather than directly behind the mic as with the SM58. The cardioid SM58 is more forgiving when the singer moves around. For loud stages and voices that need to cut through, the Beta 58A; as an all-rounder, the SM58.