Vastly! (just kidding)
Perhaps one of the other members more advanced than me can give
you the answer. (only a singer here)
My understanding, however, is that the "PG" series are built to wider
tolerances than the "SM" series, and cost less as a result.
I believe that the Peavey PVM 520i is more of an "all around"
microphone in any case-unless educated to the contrary.
Chris