I take the stairs, unless I have to carry something heavy.
I think it is a lot better for me and the environment if I use the stairs.
Also it is a faster if I was in the situation you describe or the distance was only 2-3 floors.

Downstairs I don't care about the number of floors, after all I got all the potential energy I need to get down. Upstairs I take the elevator if it is more than 6 floors.