My vote goes to the guilloche! As everyone has said, it’s much lower maintenance than MOP. And personally, I think it looks absolutely stunning on you.
They both look terrific on you and I love the multi-facet look of the MOP that you received! But I would keep the Guilloche first and then add the MOP down the line if you want to.
I know this post is late but I also love the guilloche. Also, how do you deal with the necklaces tangling? They always seem to tangle even at different lengths.