they are the same mike, except the 58 has a ball, which makes it stand more abuse from vocalists.. in general the 57 is better for instruments, but from reading, the seem to give similar results for vocals.
Unless a vocalist is very prone to popping their P's, the SM57 has more clarity.
If you switch to a '57, make sure to get a nice vocal pop screen-not foam.
They DO sound different...
Chris
P.S. BTW the SM58 is used also by a number of pro AE's for drums over
the SM57.
I would recommend buying a sm57 for any of those uses you listed.
Its like a "swiss army mic" for beginners!
Thyre still used by professionals every day for all those uses you listed as well.
I agree that when you use it to do vocals you should use a pop filter with it.
They do sound different, but they are the same mic. The reason to use the 58 on drums is because the ball can take a stick hit. The 57 and 58 are not different enough to have your underwear in a bunch about. It's like choosing between Dannon vanilla yogurt and Yoplait vanilla yogurt.