Wait. Confused, yet not so confused.

Lumens=the amount of light 1 candle gives in a square foot area.
Candela=the amount of light a candle produces.

So if this is correct, which it is, then some people are just not understanding.

The amount of lumens is important for volume of light produced in a designed area.
That is why 400w works great for a 3x3 or 3x4 or so maybe even 4x4 depending on height.
That is why 600w = more plants
That is why 1000w = even more plants.

The idiot saying lumens is not important is like saying size doesn't matter to a girl.