The Nalgenes will be fine with a little extra space to allow for freezing. Try one in your freezer to see just how much space you need.

The synthetic bottles do not freeze as quickly as metal ones, and they let sunlight through so they melt more quickly. They also do not feel so bad against the skin when frozen! I do like to carry a single walled stainless steel one for the ability to use it in a fire for boiling water or melting snow. Just a versatility thing.