The Shure SM57 and SM58 are for the most part the same mic with different grills... however, they are also different mic's because of the different grills too.
so far i have the c01 for recording.
i want to get a sm58 for live stuff.
i want to get another mic for recording mainly acoustic, i am leaning on the 603. most people in this forum think its a good mic, i'll take your word for it and try it.