In ears solve a lot of problems.
The need for ear plugs because the drum cymbals and/or loud guitar... The in ears act as earplugs, this is no longer an issue. No ringing or pain unless you had your monitors up too high.
Having Ear Plugs even with the good ones you can still struggle to hear some of the softer instruments or vocals in the mix.
Sound man puts too much of one and not enough of another in your monitor, that is it.
With in ears you can make the mix yourself. The keyboard player today is annoying, I can turn him down enough to hear and that is all that is needed, when the good one comes back turn keys up. Guitar is perfectly mixed just below the drums, Jenny's vocals are no longer ear piercing because she sings too high for my ears and Angie's vocals are sitting in there nicely.
Through all this I can hear myself fantastic.
It is the same mix every time. When needed, cut or boost someone.
The bad.
You will not hear the audience.
If you do not get in ears that can reproduce your bass well or are poor fitting it will not be fun.