It is better than the copper one because you don't really have to check if the IUD is intact... from the period quantity, you know if it is working. Mirena is a hormonal IUD, it prevents the thickening of the uterus thus the period bleeding will be less. I was told that once IUD is removed, you can get pregnant right away.

The copper one as far as I heard might induce heavy bleeding and you will have to check (putting your finger in to check the thread is still inside). For Mirena, you can guess from the amount. I am told after 6 months of insertion, the majority of people iwll not have period any more, just spotting.

Personally, my period has always been very regular, now because it is just spotting, I am not even sure if I am on the period or not. The only thing I notice is that I tend to have acne breakout once a month... just like before when I don't have IUD insertion.