Hmm lots going on here...
As to why vert isn't more popular... so many reasons... it is very misunderstood, people are very used to horizontal, and it can be more planning/work to set up/maintain... it's also a horizontal world... sometimes hard to make things meant to be used horizontally work vertically, or to find things made for vertical growing... you know that at one point people tried to popular round houses... lots of advantages (heating, cooling, other stuff I forget). Major disadvantage: nothing's made for round houses. Pipes, furniture... most stuff in that vein... is meant to go against a flat wall.
Horizontal is what we're used to, what most things are made for (planters, trays, etc etc) and whats easiest/most convenient. After all, to start my horizontal grow I just put a bunch of pots in the corner... for a good vertical, I would have had to build some sort of framework, and one sturdy enough to hold all that weight... or spent a lot of time training, depending on my route.
There's also circumstances... I have ~3'Wx4'Lx7'H space... A vertical grow would work well... I could fit so many plants!!! But, I only grow for myself. It'd would be overkill for me to do that, and it'd be a lot more work... from the planning and setting up to the taking care of that many plants... and while my return would increase (i.e.: yields to input ratio), my initial expenditure would as well, i.e.: aside from more work, I would need to pay more per month as I waited for each harvest (which would thankfully be much greater, bringing me out ahead). That's not always convenient for everyone.
For me, it works out to have a small number of plans and do a perpetual harvest, splitting my space vertically into a veg chamber on top and flowering on the bottom. My returns still save me a huge sum (at least 50% compared to buying it a the shop... and this is from a really haphazard grow and counting the cost of reusable materials... so my future grows will only improve those returns... which is more than enough for me).
Of course I have been considering vertical... but with so many options, it's hard to know what might work best for me. I've thought about dipping into it with a half stadium set up in my current space: a stair going up from the right wall to the left, with the lamp hung where the right wall meets the ceiling (opposite the rise, angled towards it/the plants... haha I should probably upload a sketch). This is mostly to give each plant more room, and hopefully more light, rather than fitting more plants... I keep going back and forth on what would work better for me, more plants or bigger ones. Right now I have six in there and they're pretty crowded.
As to the LED/HPS thing, I feel like I missed something... a) the 360 nature of high powered bulbs is
one reason people do vertical grows, not
the reason... if there is a THE reason, it is to maximize space usage. Generally speaking there is a lot of wasted space in horizontal growing... meaning space that's not really serving a purpose. People want to maximize their useful horizontal space. i.e.: you want plenty of room in your living room to move around (or sit around, or whatever) in. If you take all the stuff in the room and spread it out so no one item is on (or in) any other, it would take a lot of horizontal space. So you stack things vertically. This is also why we have really tall buildings in cities: horizontal space is at a premium... vertical space is pretty much free.
As to the lights... CFLs emit 360 degrees (horizontally
).. there are LED cob lights that do the same... or you could just as easily angle the lights. My LED grow light is unidirectional, with maybe a 45 degree spread... so two side by side, angled away from each other, could light half a circle, or a full stadium setup (which is the same thing really heh).
Huh?
Again, huh? it doesn't make any sense that you would be switching from pointing 250 watts at each trellis to pointing 600-700w at each one... yeah it doesn't. Why would you "have" to do that with LEDs?