OK, I'll try this one more time. THERE IS NO SUCH THING AS AN XLR MIC. XLR references a type of connector only, it tells you nothing about the characteristics of the mic it's connected to. A mic with an XLR connector on the capable can be of any type and have any impedance.
The Shure SM58 is a dynamic cardioid pickup patern mic with brighted midrange specifically for vocals but it is low impedance and does not work well with most modern ham rigs. I've never heard of a MC58 but Shure has a website at
http://www.shure.com/americas/products/microphones/ and any info on Shure mics is there or elsewhere on the web.
If your rig is built to use mid to high impedance mics, you're pissing in the wind with low impedance mics.