Thought this might be of interest...
http://www.homestudiocorner.com/2009/06/18/shure-sm7b-vs-sm58-with-audio/
http://www.homestudiocorner.com/2009/06/18/shure-sm7b-vs-sm58-with-audio/
I’d never thought to use the SM58 for recording vocals. That would be “amateur,” I thought.