I've heard about the copper, & where Im from they no longer use it because of the problems that it causes. The mirena is the same thing only plastic, & it lets of a small amount of hormones. I had it for a year, & it was amazing in the time that I had it. The iud's like this have strings, very small & cant be felt by you boyfriend, if he can feel them then most of the time your doctor could shorten them. It didn't interfere with my sex drive, the cramps only lasted that day, my periods were more like spotting after the first 4 months! the first couple of month's it lasted maybe 2 or 3 days. I never checked it once a month, more like when I thought about it!
I wouldn't trust copper in my body that long, but that's just me! I hope this helped!
its non hormonal, which means it wont mess with sex drive etc.