The Paragard IUD is a copper releasing IUD that is good for 10-12 years. It can make periods heavier and crampier, both of which can be handled by taking motrin or advil with the period.
The Mirena IUD is newer, and is a progesterone releasing IUD that is good for 5 years. It is 99% effective against pregnancy and patients get lighter, shorter, less crampy periods over time, and when it is in for a long time, some patients stop getting periods. Insertion is simplified, and a one hand insertion technique is used which can decrease the risk of pelvic infection on insertion as opposed to other IUDs