I wouldn't say 'big yields' so much as efficient yields. 6000 watts over E&F tables will out yield a 2000 watt vertical system that took as long and cost as much as to make (and uses as many plants). The whole theory with vertical is that a bigger canopy is better than a reflector - you still loose some light to the top and bottom though.
Thing is, %20 better light usage doesn't matter if your needing to run a 1/2 hp chiller, or a bunch of AC's, or your plants get pests that you can't deal with because you can't get to them.
Guess my point is that, before anyone goes vertical, they need to realize it isn't 'better', it's just different. It's pretty disappointing to put together a super-elaborate system, just to realize that (except in the winter), it's no better than normal ebb and flow tables.