I'm in a band that's recording now. I posted a thread not long ago asking questions about the best way to go about it (we completely scrapped micing the guitars, and I'm thankful for you're advice on that).

We are recording vocals, but we want to know what mic is recommended. We've read some things about the MCL 990 and want to know how it compares to the SM58 in your opinion? Is it decent?
In my opinion the MXL would be better for recording vocals. The SM58 is a way better live mic, but can't approach the richness of a condenser for studio work.
Too cool for a signature.
youve got better options than either of those two for the price. the mxl is an ok mic, but a lot of people dont like it that much. i think it sounds ok, and does sound pretty solid when paired with the 991 on an acoustic. but for around $100 you can pick up an at2020 which is nicer. and if you dont mind going used, you can get something a bit better. id probably go for the at2020 if i wanted a new condensor for around $100.
the mxl 990 is a very poor mic. the 58 is definitely your best bet of the 2
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The SM58 is a dreadful choice. The 990 is better, but there are much better condenser mics in the price range (the MXR has a smaller diaphragm than most 'large diaphragm' mics)