Hi! I vote YG MOP. Why?
Because the YG MOP combination to me is the bomb! The MOP just glows!
For me, I am not a fan of wearing just an "all metal" chain necklace. That's just me though.
Yes, Grace Kelly wore it, but that was a different time and aesthetics were very different then.
Today, all metal chain necklaces give off a different aesthetic and vibe, so think about your preference.
For me, I much prefer the elegance and glamour of YG MOP.
Jewelry is all personal preference, so think about your fashion look and what you prefer.
I am a huge pearl fan and have worn pearls for a long time. Pearls are more robust than you think.
I have a WG MOP set that I love and wear often. It's not like you are going to swim & soak in your 20 motif.
You will be perfectly fine. I would not let fear prevent you from getting what you love. Buy what gives you an ear to ear grin.
Just my two cents. Regardless of what you decide, I love love love the 20 motif... I think you will love it too. Good luck!