Congrats on your wedding! Without knowing what colour you'll be wearing or what colours you normally wear, I prefer the rose poudre. However, it seems more of a spring/summer colour. I have the black matte version so, I might be drawn to it because it is on the opposite end of the spectrum. The metallic gunmetal is more fall/winter and night time colour for me. However, they are both beautiful. Will you be seeing these in person? That should help you decide what will be more useful to you.
I will see both in person. On my wedding I‘ll be wearing white, usually I wear a lot of blue, grey and white colors.