Everybody knows who set "the standard" when it comes to an acceptable level of audio quality with microphones.  This is a great supercard, dynamic mic.  My primary use for it is miking acoustic guitars.  Turns out it can do pretty good vocals as well.  The biggest difference between the Beta 57, and the regular 57 is the Beta is a supercard while the standard 57 is just a cardioid.  So the Beta is also a bit hotter, and a little less muddy, if you will, while still maintaining a good level of warmth & fullness.  You can spend a bunch of money on instrument mics if you choose.  But the Beta 57 will cover a lot of bases, and do it well.  I would probably opt for the standard 57 for miking electric guitar amps.