What is the difference between a copper IUD and a hormonal IUD? How does each one work exactly, and why would someone choose one over the other?

Sharon

The copper IUD, called Paragard, is FDA-approved for 10 years of use, making it incredibly convenient and also inexpensive if used for the full 10 years. The hormonal IUD, Progestasert, contains progesterone. It must be replaced every year. Both IUDs are excellent at preventing pregnancy. Both can lead to heavier, crampier periods, although this is more likely with the Paragard (copper) IUD. Both are normally given only to women in long-term, mutually monogamous relationships, as these women are presumably less likely to contract sexually transmitted infections.
As to why one over the other, that is a very personal and individual decision. Some women prefer the Paragard because it can be used for 10 years. Some prefer the Progestasert because it is less likely to cause cramps, or because they are considering a pregnancy in a year or two. Only you, with input from your doctor, midwife or nurse practitioner, can decide which IUD -- if either -- is best for you.