AC: Leave basement vents off or on?

[Red Squirrel]

I was thinking, I should shut all the vents downstairs so the AC only goes upstairs as that's where it's hot.

Then I started thinking, if I open up all the vents downstairs it will help push the cool air from downstairs upstairs. Which way do you think is more effective for maximum cooling efficiency?

 

[funkymatt]

hot air rises...

 

[Amused]

You want to leave at least most of them open to dry out the basement air and prevent mold.