All I can tell you is I've used a SM58, live, for about 2 years.
Now I upgraded it to a Beta58, and WHAT A DIFFERENCE!
It's like the SM58 was making the voice darker...
The Beta58 makes the voice much more natural, brighter...
I really don't like the Sm58 now... Buy a beta58 if you can, otherwise you may try another brand then Shure.
Luis Santos