The difference is your water and block will be colder than ambient if you're doing it inside so it will start getting wet with condensate. If you have your whole rig in the cold it cant condense because everything is at or above ambient temperature.
Edit: @
Durvelle27 you linked to an EK supreme, the Supremacy blocks are the newer version of those. theyre supposed to do a degree or 2 better.
It's like 15 degrees F here again, and getting colder every night. Something like -10c I think. I'm afraid to move my rig outside, I'm scared my water might freeze or something, lol.
Edit somemore: does it update you if I @ your name like that?