Which IUD?

So this is the first time I'm going on BC and my only options are the IUD but I want to know which one is best either Mirena or the Copper one (ParaGard)? I don't want to use pills because my mom doesn't know I'm gonna go on BC she's really strict about sex in general so I needed something a little low key! So if you guys have any suggestions on which IUD please let me know!