a vocalist will most likely be using a 58. 57 is more directional for instruments.
we buy better than them because we are junkies. most bands will put their money into instruments and FX over mics, and there goes the budget. a 58 is really quite adequate and extremely bombproof. our mics are a bit more expensive, and more delicate, than a gear provider wants to invest in, when they have cases that hold 18 or more. Some bands do travel with nice mics because they know how well they'll perform, but it is rare, and food and fuel must be purchased.
my .02