If you are gonna grow a trees, i would say kool tubes...

If you are growing in a closet and wanting to light a canopy top, I would use white because I think it reflects better on the 3 rebound.

I think straight up reflectivity may not be as high at say mylar, but what people fail to realize, is light continously travels until ALL energy is dissapated.

I just think white is better suited for constant bouncing because of the diffussion.