Thank you, Tone and Boydie.
1. My reason for choosing the Sennheiser turns out not to be valid--I want mics with on-off switches. The SM58 I was looking at didn't have one, but I see there is a slightly higher-priced one that does have the switch, so never mind about that detail.
2. I have recently started practicing with two other women, and we have a sort of gig coming up on October 22 for a Bahá'í event. We're entertainment for the event, but we're not the event ourselves.
3. I doubt I'll have a chance to compare how the two mics sound to me. There is a small music store about 100 miles from me, but I don't think they would open packages and let me try them. I could try a pawn shop in the same town, but their selection isn't great at any given moment, so I don't know if they would have anything to try. I could look, though.
I already have two Shure mics, but they're about 30 years old. The interior wind screen has crumbled to dust in one of them and the other one quit working. I have taken the interior wind screen out of the non-working one and put it in the one that still works, but we would still need two more mics. So I'm shopping.
Thanks for the input.
Vicki