Shure 8700 C-series

[dari]

hi all,
i bought this shure microphone a few years ago: http://www.shure.com/pdf/userguides/...s/c_series.pdf and i've been told the SM58 is much better.
the thing is both have a frequency of 50 to 15000... what is the difference between them?
also, i heard that you need a preamp to make a good use of my microphone, but not with the SM58. is this true?
i really tried to understand the whole thing about microphones, cables, preamps and "phantom power" but it's really chinese to me . hopefully i'll learn in time, but if someone could give a hand here to decide whether i should buy an SM58 or a preamp, i would really appreciate it
Thanx!