The Sierra Designs Nitro 800 is a better bag all around because it has a zipper/draft collar making it more thermal efficient and thus warmer for the same weight:
https://www.massdrop.com/buy/sierra-designs-nitro-800fp-sleeping-bags
I've requested the Nitro 800 drop be reactivated. If you feel the same about it, click "Request" on the above link!