I considered Paragard because I like the idea of birth control without hormones. I ultimately decided against it because we are planning on trying to get pregnant about a year from now, when our daughter is 2, and it's more of a long-term method than I'm needing. IUDs can stay in place for several years! We are unsure as to whether we want to have one more baby or two, but when we are done I may get an IUD if DH won't get a vasectomy.
Unless you need help regulating your cycles, I would go with the Paragard over the Mirena (which contains hormones). I like the idea of things being as 'natural' as possible, but that's just me. That said, I am using hormonal birth control right now (Nuvaring) because I have PCOS and the irregular cycles that usually accompany this syndrome.
That's my take. If you get an IUD I hope you love it.