So correct me if I'm wrong, but one should be able to (+-) double their sq/ft coverage w well designed vert system.
Math:
Horizontal (Mag XXXL) gives soild 5x5 = 25 sq/ft
Vertical: Is the surface area of a cylinder (not incuding top & bottom) gives 2*r*3.14*h (I assume the bulb would be 2' from the plants and the height of the plant is 4') = 2*2*3.14*4 = 50 sq/ft.
Are the distances used correct? That the radius is 2 feet and the height is 4 feet? If so I need to do a vert grow! And not only b/c I can increase sq/ft, but this would fit better in the space I have, which would allow me more room to move around plants.
If I were a large scale and/or have lotsa space I can see the simplicity of horizontal, ecspecially over 4x8s as Avant is going to do next. Who really gives a ef about whether or not you pay 3k or 3.5k for electric and need a few extra lights if ur large. Its the CODB. What matters is how much net $ and how fast it moves.
I run vert with two bulbs stacked with 50 square foot of canopy in a 5 X 7 X 7 room. That is 50 square feet of grow in a 35 square foot room and I still have room to move around.