You’re right! The Messika is also definitely more stunning in person, I also agree that small dainty pieces with diamonds have a great balance between size and sparkle ✨While neither are my aesthetic and I personally tend to go for more classic styles, I choose the Messika.
The Chaumet feels a little...meh. Honestly from the photo I couldn't even tell it was MOP. Looked like white gold to me.
Also, diamonds over MOP any day lol.
Generally with smaller, more dainty, less statement pieces, I feel that the sparkle of diamonds give it that little extra oomph. It helps it stand out a little more, a sparkle here and there, without being too much.