Flowering Room Size?

Hey Guys.

i cant decide what size ill have my flowering room at. I will have a 400w HPS in it. What size would be better and why?

3'dx3'wx7'h
3'dx4'wx7'h
4'dx4'wx7'h

Thanks.

Bump.

I'm going to go with the 3x3x7. Will that measurement of the frame be from the inner or outer?

Thanks.