I would go with the mirena out of the two choices you provided. However, I have had outstanding success with the
Nuvaring for about 10 years. It is simple to use, keep it in for 3 weeks, take it out for one, then put a new one in. I had no side effects whatsoever, which was different for me than other birth control methods. It regulated my period out to where it was like clockwork. If you forget to take it out or put it back in on exact times, the risk of pregnancy is very low.