why top downs ?

[fooser]

Originally Posted by BlueAbyss

I believe I have heard it is because the light comes from above, and so the pigments are more concentrated from that angle. Not sure where I heard this though, consider it conjecture.

Originally Posted by Snaz

What is more likely is some light never gets through the glass, compare to the glass shield covering a MH light blocking 80% UV light.

I believe that both of these are true and that when put together, makes and even bigger difference to why they look better top down. If you look at a coral in your tank at a higher angle (but not top down) it will look different than if you looked at it level straight on, and that will look different than if you look up at it from an angle below (crouching below eye level of the coral).
Interesting topic to bring up John.