Thought some people may find this interesting, it's a shootout between the Shure SM7B and SM58. The guy reveals the results in another link, but see if you can guess. They come pretty close I reckon.
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/