Disadvantages to pads. Since they're outside your body, the blood can get in contact with air, and a pad left on for a long time may develop an odor. How much of a disadvantage this is, if at all, depends on your activities and your attitudes. If you never go near a swimming pool, you never wear tight pants or leotards, or you don't care if someone can tell you're menstruating, this won't be a problem. Of course, you can avoid this by using cloth pads that you wash and reuse, but then you have to factor in the cost and energy of the washing.
Some women are concerned about hazards from the chemical used to bleach many disposable pads.
A few companies do make unbleached menstrual pads, disposable or reusable. Some women find that pads chafe their inner thighs. This can sometimes be helped by switching brands or changing to another type of pad. Pad Links Gladrags Reusable cloth pads. Natracare Chlorine-free cotton pads and tampons.