It doesn't leak at night as pads do, it's cheap and environmentally friendly, but mainly that it doesn't dry out my mucus membranes and doesn't contain bleach and pesticides that I don't want anywhere near my uterus.
Best protection for one who works in white clothes all day, never had a single problem and soon my whole department will buy one (I work at a hospital) each!
A small revolution is what the menstrual cup is. No purchases, no smell. Freedom to just be for a whole day, no waste, always available, no chafing, no itching. Simply the best!