Hi Btherl,
Seems like you're looking for a microphone for live use?
Basically two main things to consider at this stage:
1) Type of microphone (dynamic? condensor? ribbon? etc.. both SM58 and Q7 are dynamics)
2) Polar Pattern (how, where the mic picks up it's sound)
SM58 has a cardioid polar pattern, whereas Q7 has supercardioid (picks up less sound from the sides, but a little bit from the rear-end). You can't really go wrong with the SM58, but take a look at the Shure Beta58A as well - very nice frequency response (more detailed sound than the SM58 - and also hotter level before feedback). Beta58A is slightly pricier than the SM58, but it's worth the extra bit.
I haven't tried the Q7 before, but do have a look at microphone types online. There's loads to say about microphones, but it really boils down to your application and budget.
Again, you can't go wrong with the SM58 heh trusted brand lah. Cheers, good luck.