Ive always found it a safer bet to buy 57's new from an authorised dealer. there are a lot of fakes out there58 is the Standard for Vocals. The 57 is the Standard for Cabs & Snare Drums.
It's comparing Apples to Oranges however. If you're considering buying just one new, it may be better to look in the Emporium or your local Craigslist, because you can find either used for around $60 +/-.
Then....change out the the 58's Grille Cover (about $5...)so you have a fresh grille to sing into.
So, for about $125 (or less), you can have both great mic's that will last darn near forever..for just a little more than the cost of a new one.
Yep....they're cheap enough new...too risky 2nd hand, i would at least see them in person first if you were buying 2nd hand, since they're both the most counterfeited microphone in the world...Ive always found it a safer bet to buy 57's new from an authorised dealer. there are a lot of fakes out there