What is warmer?

I know warmth is subjective so not a specific temperature but in general.

An atom or a 2017 cerium they would both be under a shell?

For sake of discussion assume no issue with sweat making the down wet so the cerium retains 100% of insulative properties and proper base layers.

Never been a fan of down skiing but these extreme temps are making me consider it.

Edit: being I already owned it I skied in it today and for someone like myself who runs cold it was great. I’ll stick to my atom 95% of the time but it kept me perfectly comfortable in the frigid temps.