The Shure PG58 is one of Shure's new budget range of performance mics and is designed for stage vocals.
Like the PG48 it is quite bulky to hold and not as clear as the Sennheiser e825s. The PG58 does not suffer from wind noise and has low handling noise but with the same token it doesn't have as much bottom end and means the bass can sound a little floppy. To be honest, listening retrospectively to the PG48 and PG58 I couldn't tell the difference between them but maybe you can!
If you've got your heart set on a PG58 then take my advice and be sure to compare it with the Sennheiser e835 and e845.