The Cosmos is gorgeous but I'd think you'd be limited in your choice of clothing. The all-diamond is neutral and you could wear whatever colour you like!
And also IMHO (mine only, of course), the Cosmos is more grown-up whereas the Frivole is more "girly" (and therein lies my own "dilemma" also, lol). So, it'd depend on your age I'd think; or maybe I'm wrong (I reeeally hope I'm wrong about this, lol).
Voting for the first one as well -- seems easier to dress up/down. The cosmos, even with less bling, somehow seems more formal, and might look best with a long gown.
Are you getting for everyday wear (well, maybe not for hot yoga or gardening...), or more for events / nice dinners?
I vote for the first one too. It sits on your fingers really pretty and how could I miss the bling factor. I like the cosmos, somehow it has more laid back vibe (maybe black enamel has to do something with it) but I find the gap between the two ...not so easy on the eyes. Good luck deciding.
Hands down, the Frivole! On top of being more versatile, I'd worry about the onyx on the Cosmos getting damaged when washing your hands or if you were to bump into something. Then again, I'm extra clumsy.
The another reason for choosing Frovole is that it is less "fashion jewelry" look (I know I know, but for people do not recognize VCA design, it might happen). For example, I wear my Tiffany dragonfly brooch often when my dress or top is a solid blue or black color. This morning when I was at the coffee shop that I have been daily visited, the female owner who is also quite fashionable, told me the brooch I am wearing is very pretty. It is the Tiffany iconic platinum and diamond dragonfly - medium size, which I had shared it here in "Tiffany Forum" before. She aslo asked me if it is a Swarovski brooch, and I told her that it is Tiffany. https://forum.purseblog.com/attachments/img_5647-jpg.3604134/